IAQ: Mystery Odor
Q: Occasionally (maybe when our heater kicks on, but not every time?) I smell a chokingly strong odor, very similar to the smell of a hot vacuum cleaner with a full bag where dust seems to be bypassing the filter, plus a little bit of burning dust in a space heater, plus maybe some urine smell. Weirdly, I'm the only one who smells it. Others in the house are unfazed. It goes away after three or so minutes. I've changed the air filter on the heater and we've had the ducts cleaned to no apparent effect. We have had some problems with mice but I haven't noticed a correlation between mouse sightings and the occurrence of the smell. So, 1) Does that sound like any kind of indoor air quality problem you're familiar with? 2) Do you know of any indoor pollutants that only some people are sensitive to, or with an extreme differential in individual sensitivity? 

A: Re Q#1; never had this one before (although a significant number of the questions I have gotten are unique.) For Q #2: I think it's unusual for one person to smell something that others can't, but in the world of reactions to mold, some people can walk into a horrific infestation without being bothered, while others are unable to enter the home. It's possible that there is a dead critter in the ductwork. However, the possible association with the furnace raises the possibility (probably remote) that combustion gases are entering the building or ductwork.

The two possible mechanisms are 1) Corrosion in the heat exchanger, allowing direct communication between the furnace firebox and the ductwork (this is a potential/inevitable happening at the end of a furnace's lifespan, about 20 or so years). It is hard to overemphasize the importance of CO alarms, especially in houses with aging furnaces (although a well-tuned furnace may not produce a lot of CO). A visual inspection of the firebox/heat exchanger might reveal any corrosion or opened seams in the latter. 2) There is the possibility of backdrafting: When multiple exhaust or vented combustion devices (water heater, clothes dryer) operate simultaneously, if sufficient replacement air is not provided, the resulting vacuum can set up a reverse flow in the weakest appliance, pulling combustion products back in. This can sometimes be detected by holding a piece of tissue paper near the opening of the flue pipe as it exits the appliance. (A small 'puffback' at startup is normal before a robust draft gets established in the chimney.) A partial obstruction in the chimney can also cause backflow of some combustion. For oil-burning equipment, backflows will have a prominent odor of burning oil.

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Tsartlip First Nation Success Story
This week's FAQ is, well, not exactly a question but something else that you might find interesting.
-Joseph T. Ponessa, Ph.D., Professor Emeritus, Housing, Indoor Environment and Health, Rutgers Cooperative Extension

In their most recent newsletter, the Canadian Mortgage & Housing Corporation, an entity of the Canadian government, describes a "First Nations" program there that may have relevance in this country. The Tsartlip First Nation is a community with some 165 housing units on the reserve, situated in British Columbia not far from Vancouver. Many of these were rental units. In the late 1990's. it was recognized that many of the houses had mold problems. With some help from outside funds, some 40 homes were remediated, and an additional 10 units were demolished. During this process, a listing of common problems leading to moisture issues was developed. At the same time, it was recognized that the average cost of renovation to solve the mold/ moisture issues was unsustainable.

Thus, a decision was made to build capacity within the community not only to remediate mold and fix the problems that caused the mold, but also to address the causative problems in future new construction. A construction crew of 20 tribal members was hired, along with a project manager, hired for three months, who would also provide training. (The project manager ultimately stayed for many years.) Workers did not have previous formal construction knowledge. A local crew supervisor, who knew the individuals, proved to be a valuable link in the success of this program. Eventually, the crew was organized into specific groups, based on their various individual skills and talents that emerged. Ultimately, over the course of several years, these crews and individuals took on jobs off the reserve, as well as on reserve. Work continued even after the original funding ended. In all, some 39 new homes were built over the course of several years. These homes were built to a higher standard than before, incorporating many features to minimize mold and moisture problems. 

Not only have the workers attained a good livelihood, but the excellence of their work has brought a visible sense of pride and as a side benefit, residents have learned much about good practices to minimize moisture problems in their homes. 
For more information, go to the CHMC newsletter (Feb. 13, 2012) at  http://www.cmhc-schl.gc.ca/en/inpr/enews/index.cfm to find a link to a paper on the Tsartlip project.

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Radon in the Home (Updated 02/14/2012)
Q: What are some of the mechanisms that draw radon into a home? What are some good strategies to encourage people to do radon testing in their homes?

A: First, some basic facts: Radon is a radioactive gas that is colorless and odorless. It seeps out of the ground and can collect in buildings. Its only known health effect is to increase the risk of lung cancer. Radon is present in every state in the country, with some areas having high concentrations of this gas. Radon causes more deaths than any other indoor pollutant.

While radon may be distributed throughout the house from the basement by HVAC ductwork (notoriously leaky) especially if the basement is heated, other factors come into play as well. Homes without ducts can have radon problems as well. During the heating season, one important mechanism is thermosiphoning. As warm air rises in the building, it leaks out through the many small openings, cracks, etc characteristic of nearly all buildings. This creates a negative pressure in the lower portions of the building, drawing in outside air and air from the basement since there is typically good communication between the basement and first floor. Thus, radon is distributed to the living space. These negative pressures are also an important driving force to draw any subsurface gases, such as radon, into the building. Other important factors in generating negative pressures in buildings include vented combustion equipment- clothes dryers, hot water heaters, range vent fans and the furnace or boiler, except for 'sealed combustion' units. It is helpful to understand that these driving pressures can be very small-a few pascals are sufficient; likewise very small volumes of radon (on the order of a few cc's per 24 hours) can cause problems. Because of these (and numerous other) variables, radon levels can vary from day to day and hour to hour. Warm climates homes also have radon problems. Check EPA's radon map (State maps are also available.)

The most important determinant of radon levels in a building is the geology beneath that building: hot rock beneath-likely high levels above. So there can also be dramatic differences between neighboring houses; thus, each house must be tested. How to communicate radon's importance? This is difficult, for a number of reasons: it's 'natural' and therefore less fearful to some, even though it's radioactive, which usually amplifies the fear factor; and it lacks immediacy-lung cancers take 25-30 years to develop. On the other hand, it is arguably the most lethal of indoor pollutants-18,000 to 22,000 excess US deaths per year (smokers' risks are multiplied by radon exposure); it's easy and inexpensive to test for, and fixing the problem can be readily done for about $1500 to $2000. I tell people that it's like having a smoke detector-while you may not have a problem, you can easily find out if you have a serious problem for only a few dollars. Another concept is that, if there are 'high' levels in your state-30 pCi/l or more-such homes would exceed the OSHA limit for workplace exposures. They would be shut down if they were uranium mines! Wouldn't you want to know this if you were living in such a home? It's easy to find out with a simple and inexpensive test. Your State radon office can provide additional information on radon, both general and local. 

Update: The following is a comment from a reader and Dr. Ponessa's response.

Since there was mention of a smoke detector and the very commonly installed type has concerning radioactive components, I thought of sharing the information: ATP://ecphoria/radioactive_fire_detectors

Thanks for your comment! I really welcome comments and questions relating to my FAQ's and to other housing/environmental issues. Regarding ionization smoke detectors (the most common type), this raises a good point- these contain a small amount of Americium, a radioactive element. However, in the several decades that I have worked on radon issues (and smoke detectors) I have never seen any concern expressed that the use of such detectors poses a health threat in homes. The important take-away message, to the best of my knowledge, is that these devices should be disposed of in a responsible manner. At the end of their 10 year life span (manufacture date is on the back of the detector) I take the detector to my county's hazardous waste center (you might also send them back the the manufacturer-ask first.) Do not discard in a landfill, and do not send to an incinerator.
It is difficult to capture (and explain) all of the significant facts about radon in a couple of paragraphs.

The concern about smoke detectors brings to mind another fact that provides a valuable perspective: According to the National Council on Radiation Protection report (1987) on exposure of the US population to ionizing radiation, 84% of our exposure comes from natural sources, with about 2/3 of this attributed to radon. Thus, if you are concerned about exposure to radioactivity, you should know that about 54% of our exposure comes from radon. This is a pretty powerful argument to test for radon, and to fix high levels.

Another comment, sent privately, stated that my posting suggested that radon problems mainly affect homes with basements. It was pointed out that homes without basements can have radon problems too. This is quite correct, and I apologize for not making this clear; the original questions that I responded to directed attention to basements, and my later posting should have made it clear that homes on slabs can also have serious radon problems. Likewise, homes in warm or tropical climates are also vulnerable to radon intrusion, (I believe this applies primarily to air conditioned, enclosed structures.) Ultimately, the intensity of radon release immediately beneath the building is nearly always the most important determinant of indoor radon levels. Again, thanks for your comments!

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High Relative Humidity and Window Condensation
Q: My husband and I live in Montana and we have a small (1300 sq. feet) home and an apartment (700 sq. feet) above our garage we rent out.  The apartment is totally new construction, about two years old, and the home has been totally remodeled in the past several years.  The problem we are having in both locations is excess moisture in the winter that is ruining our windows.  The humidity in the home reads about 46% (on one of those combination clock, temp, humidity devices you buy at a place like Sharper Image); I’m not sure what the humidity is in the apartment.  Both the home and the apartment have wood windows that have become so wet that the clear finish has worn off and black mold is growing.  In the past, I’ve taken steps to remove the mold as best I can but it has stained the wood beyond repair.  For the past couple of weeks we’ve left both bathroom fans and the stove fan on all day and that seems to alleviate the moisture a small bit.  But we don’t want to do this all winter and we don’t want to ask our renters to do it either.  In the home we are experiencing this mostly on the second floor, where the main bath and our bedroom is; the apartment is on a second floor as well.  We’ve been told that air exchangers are our only option.  We’ve been given the price tag of about $6800 for two of them (that includes the installation and the professional discount we would receive as my husband is a contractor).  My questions to you are:  Are these exchangers our only option to alleviate the moisture and the window “rot” we are experiencing?  Will these exchangers lower the humidity to a more livable level?  What do you think of that price?  Any feedback would be greatly appreciated.

A: There are multiple aspects to this problem, but it definitely needs to be addressed. In no particular order, here are some thoughts: 1. I presume the humidity reading is correct. Assuming it is an electronic hygrometer, these are pretty reliable, although initial calibration may be off. It would be useful to test it, such as taking it outdoors in a moderate-temperature rainy day & checking for a reading of 100% RH. Alternatively, you could place it in a plastic bag, along with a cup full of water, wait a while, and look for a 100% reading. (I don't know if the device would function properly outdoors in Montana in January, but you would expect to see readings near zero outside on a cold day).

2. The windows should be at least double-glazed (or have a storm window). Triple glazing is probably more suited to MT. At 46% RH and an indoor temp of 70 deg F, condensation will occur on surfaces at about 43 deg F, the dew point for these conditions. So if the window surface temp is 43 degrees or below, condensation will occur.

3 If the hygrometer is wrong and moisture is higher than 46% RH, you need to look for a source of excess moisture. Many sources are obvious, some are not. One big source is unvented combustion. The furnace should be checked for backdrafting. Sometimes in cold climates, the large amounts of moisture in the chimney will freeze as gases cool in the upper parts of the chimney, blocking exhaust. Another cause of high humidity is a humidifier whose control malfunctions, causing it to operate continuously.

4. The ventilation devices-Heat Recovery Ventilators-are generally a good idea, but sound considerably overpriced. They provide ventilation while capturing most heat in the exhaust stream and remove heat from incoming summer air. An alternative would be to install a short duct with a timer control to bring in outdoor air to the return duct of your furnace, assuming that this is an accepted practice in your climate, and assuming that your house is too tight.  This will have an energy cost, however.

5. Some possible solutions include: a) adding a plastic storm window (or insulating window treatments) to minimize room air reaching the cold glass surface. Briefly, the expense of doing this relates to appearance; functionally, anything that creates a small airspace from the window-poly film, vinyl or rigid acrylic-will likely solve the problem, but the cheapest will be the ugliest. b) You could also try running a dehumidifier, but this is costly to operate. You might put some effort into reviewing moisture sources in the home, against the possibility that your hygrometer is not accurate;  you should be able to find lists of moisture sources in the home on the web, or in your Extension office.

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Moisture in Crawl Space
Note: The original question involved a damp crawl space (location: Delaware) and possible solutions: using a commercial device to suck air from the crawl space, creating a negative pressure there; or sealing off the crawl space and dehumidifying it. It was noted by Dr. Atiles that negative crawl space pressure can draw radon into the crawl space, as well as outside moisture during warm summer months. Dr. Jorge Atiles (Cooperative Extension, University of Georgia) contributed initial information to this discussion, and subsequently forwarded it to Dr. Ponessa. The following Q & A is a follow-up question from the client and Dr. Ponessa's response.

Q: I'm going to move forward with a closed crawl space with insulated walls, and a dehumidifier. One concern I have is that dehumidifiers don't operate effectively during cold weather. I was wondering whether anyone studied using a blower to move attic air to a crawl space. I took a few random temp checks at my home and found a temp differential of five degrees between attic and basement on a 50 degree day. It would seem to me that attic air is normally drier than basement air (all the mildew issues appear to be in a crawl or basement environment). Does importing attic air from October through May to a crawl space make any sense?

A: A closed crawl space is generally a good idea for moist, humid (summer) climates, since ventilation during these conditions introduces more moisture than it might remove. However, it is not unusual for unexpected factors to come in to play when applying novel solutions to such problems; therefore, it is important to do regular inspections of affected areas. This will help identify any problems that may not have been anticipated. It might be worthwhile to invest in an electronic hygrometer (available in electronics stores for about $40) to check on moisture levels; generally, these should be no higher that 50-60% RH in conditioned spaces.   

The problem with basement (or crawl space) dehumidifiers is that, due to the low temps in the basement, their coils may frost up. You can buy models with a defrost cycle, but it may be worthwhile to simply operate a conventional unit for a while, checking regularly for frost. I had used a regular dehumidifier in my own basement, together with a heavy-duty cycling timer that shuts it down for 10 minutes every hour. Three years ago I omitted the timer and have not noticed any problems.

A colleague in South Carolina was able, in a one -story rancher, to direct hot air from the attic into his basement to accomplish dehumidification there during the summer. (I doubt that you would see much benefit from October through May.) A large fan was used to push hot attic air into the basement, and he found that operation for just a couple of hours in the afternoon was sufficient. Some precautions: make sure there are abundant openings in the attic for replacement air to enter, and the same in the basement. Any imbalances in air flow can cause pressure differences that can cause problems; e.g., suction in the attic can draw air from the house and, if the AC is on, you lose efficiency and, by drawing outside air into cool rooms, may get condensation on cool indoor surfaces. Pressure or wind in the basement/crawl space may blow out pilot lights if equipment is located there; (suction in basements/crawl spaces may cause backdrafting in flues, as well as bringing in radon.) Be vigilant!

AND... first of all: do the easy things to keep moisture out of a crawl space: Cover the soil with 6 mil poly and make sure rainwater does not pond near the foundation. Other tips, mainly for basements, can be found at http://www.rcre.rutgers.edu/pubs/publication.asp?pid=FS257

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Plants and Indoor Air Quality
Q: I work at a school as a para-professional and indoor air quality in the classrooms is always a concern. I read an article about plants in offices and it discussed the fact that some plants can actually improve air quality and it said it got it's information from NASA. Is there a way I can get information on such plants? Which would be the best to use? Do the plants have to be a certain size per square footage?  Are the plants harmful at all as far as allergies to touching or ingesting? 

A: Some early work was done on this topic in the late 1980's by a Dr. Wolverton and was funded by NASA. He identified certain plants, such as spider plants, golden pothos and several other common houseplants as having the ability to remove formaldehyde and other volatile organic compounds (VOC's) from the air. Subsequently, vendors have been marketing things like indoor greenhouses as air purifying systems, and a trade association had, at one time, hired Dr. Wolverton in an effort to promote this idea. Meanwhile, other researchers have looked into this issue, and Wolverton's data, and concluded that, while this works qualitatively - plants can absorb some VOC's - the numbers don't work out. If a serious VOC problem exists, an impossibly large number of plants would be needed to remedy the problem.

Certainly, plants can be a great indoor amenity, and they may provide a small contribution to indoor air quality. The downsides are that: 1) some allergic occupants may be bothered by the plants; and 2) the damp soil may be a breeding ground for mold. Remember too, that virtually all the water provided to a plant is ultimately put into the air by the leaves. So an 'excessive' number of plants can lead to a moisture problem.

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Invasive Fungus
Q: I have an invasive fungus that is growing into my home. It started in the dirt under the house and is growing into the construction of the house now. What is it and how do I get rid of it?

A: From the brief description, it sounds like a growth of Poria incrassata (or related species), “The house eating fungus.” It’s found throughout most of the US, but is particularly common in the southern coastal states & the Pacific coastal areas. There is a pretty good description (although somewhat dated in a few details) in this book chapter:

Basically, this fungus can grow in a damp crawlspace, often getting its start on wood construction debris left there. The key feature of these molds is that they send out long growths (rhizomes) that can enter walls, extending even to the second floor. The key mechanism is the capability of these growths to convey water (from the earth) along their length, allowing continued growth as wood is consumed. Ultimately, serious structural damage results. The simplest cure is to cut these rhizomes, provided that there are not other sources of water in the walls (such as from condensation or leakage). Some chemical treatments are also effective.

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Vapor Barrier & Insulation in Crawlspace
Q: My crawlspace is damp and smells like mildew/mold; it has been this way for a while. We have a high water table in our area. I just received a quote to have a vapor barrier and insulation installed; the crawlspace is 1,000 sq. ft. This quote included 20 mil poly and some type of reflective thermal insulation. The quote was for $6,000. I had another outfit come in to give me a second quote. They are quoting the same work, however, they will be using 6 mil poly. Here are my questions: 1) Does $6,000 sound like it's in the ball park for this kind of work? 2) If mold is present in the crawlspace, what should be done (if anything) before the vapor barrier and insulation are installed? 3) Is 20 mil poly recommended for the vapor barrier, or is 6 mil poly sufficient?

A: For the vapor barrier, 20 mil sounds like overkill. However, this might be appropriate if there is 'traffic' expected in the crawlspace; for example, to service HVAC equipment located there. More customary is 6 or 10 mil, placed on the ground and overlapped 6" or so. The best applications involve carrying the plastic up the foundation walls for about a foot, sealing it to the walls. This strikes me as a lot of extra labor for, probably, a small benefit.  In any event, though, this stuff is cheap relative to the labor involved in installation.

I don't know much about costs for doing the plastic or installing insulation; getting a couple of bids, for the same specifications, seems like a very good idea. The area involved is, obviously, an important factor. Also important is the headspace available. If it's three feet, installation is a lot easier than if it's 18 inches.

The high water table is a tough issue to deal with. If liquid water is regularly seen (and gutters are performing properly, and there is proper grading away from the building) a sump pump might be in order. Local practice can offer some guidance; if neighbors have them, and if they improve things, then this might be part of the solution. But a plastic ground cover (and proper rainwater disposition) are the first steps.

If mold is found, it should be removed. This needs to be done safely, by someone who knows what they're doing, so that the rest of the house is not contaminated, and neither workers or occupants are exposed. Killing the mold is not sufficient if there are large areas involved-more than 10-20 sq ft.

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Lead and Children (Updated 11/9/2011)
Q: How much lead can hurt my baby?

A: The amount of lead that can cause damage to the developing brain in a young child is extremely small. Since lead is a cumulative poison, it doesn't have to be eaten (or inhaled) in a single dose; tiny amounts eaten each day, in traces of lead-contaminated dust ingested as kids chew on hands and toys, can deliver a harmful dose. Problems later in life include impaired learning, attention span difficulties, decreased IQ and behavioral problems. Through all of this, the child doesn't look sick, so parents have no idea that anything is wrong. 

So how much lead does it take? Twenty micrograms per deciliter of blood (mcg/dl) is considered a danger level, although problems have been identified at levels less than 10 mcg/dl. To help understand how much lead this actually is, I have calculated  this amount of lead for a 10 kg baby (about 22 lbs.) assuming even distribution in all body fluids and it works out to about 1.2 milligrams of lead. Paint from the 1950's could contain 50% or more of lead by weight. So I weighed out 2.4 mg of old paint and the pictures below show what this looks like. 

As mentioned above, this amount of lead in a baby's body would be a significant danger for this child's future development. This doesn't have to be ingested all at once; tiny amounts of contaminated dust or soil, eaten regularly, will do the job and the child will never look sick.

lead1 lead2

Update: Here are a couple of pictures of an old paint can, showing the product's composition and weight: 88% lead carbonate, 55 pounds. While the pictures do not clearly show the scale of the cans, they are a bit larger than a modern, 1 gallon paint can. This paint was commonly used through the 1940's, and to some extent in the 1950's.

hhhhh lead paint2

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Chimney Moisture Problem
A: I was searching the internet for information on roof leaks and found your article in Home Energy, "Solving a Chimney Moisture Problem". It sounds so similar to my problem. We have a leak coming into the attic from the chimney area. We've waterproofed the fireplace and reflashed the chimney and, still, it is leaking. Our roofer was so puzzled by this it kept him up nights. One chimney company said we needed to cover the fireplace brick (new facade) in order to stop it. We are at our wits end; we've spent so much time and money on this and nothing solves the problem. It seems to be worse in the winter and the roofer seems to think it has something to do with our furnace. We converted to gas when we purchased the house and both the hot water heater and our furnace are vented through the same flue in that chimney. Two years ago, when we were sealing the chimney, we noticed water in the basement near the bottom of flue. Upon inspection, the flue vent tech saw it was damaged and the furnace company came back and replaced it with an aluminum flue. could this still be causing the problem, maybe the flue is not sized properly or maybe both appliances should not be vented together? Can you help in any way? We are really desperate!

A: As my article points out, the problem in that case was a partially blocked flue; squirrels had built a nest in the chimney, mostly blocking the passage of combustion products. Combustion of fuel (or any hydrocarbons) produces water. A lot! I don't remember the exact amount for natural gas, but it is on the order of 1 gallon (!) per hour of firing for a typical residential furnace/boiler. Since combustion gases for gas heaters are typically cooler than those produced by oil-fired equipment, there is the tendency for condensation in the chimney. This is probably more likely with newer equipment, which is more efficient than older, squeezing more useful heat out of the fire, and sending less up the chimney. Some ultra-high efficiency furnaces extract so much heat they can be vented like you'd vent a clothes dryer, and are equipped with a condensate pump to get rid of this moisture.

While a blocked chimney might explain your problem, it is also possible that combustion gases from the newer furnace reach their condensation point before exiting the chimney. If the problem is worse on colder days, this supports this idea. (The chimney can be checked for blockage by turning off the furnace, disconnecting the flue pipe & placing a mirror in the opening; you should see sky, unless the chimney is offset.) if the problem occurs on rainy days, then rainwater is probably at fault.

An aluminium liner may have helped somewhat, and is also important for safety reasons. If condensation is at fault, it may be possible for a technician to fit the flue pipe with a booster fan to speed the exit of combustion gases before they condense.

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Cooking Smell in Home
Q: I'm a prospective home buyer and I want to know whether I should risk buying a house that reeks of curry. The current owners do a lot of cooking with Indian spices, including curry. Do you think I will be successful in getting out the smell? If so, how?

A: While I can't absolutely guarantee that this would work, I have recommended the treatment of house odors based on the remediation that is used after a house fire (to get rid of residual smoke odor, after the soot has been physically cleaned): Hire a firm that does fire damage restoration/cleanup to provide an ozone treatment for the house. This is done, of course, while the house is unoccupied. This method is used in hotel rooms also, when a smoker has occupied a non-smoking room. Although ozone is a strong pulmonary irritant, it is a highly reactive chemical that dissipates quickly and should pose no lingering threat. A 
good airing afterwards should dispose of any byproducts of ozone reactions with volatiles in the home. It would be best to do this treatment in an empty house as much of the odor may have penetrated upholstered & fabric furnishings and the ozone treatment may not be fully effective on the furnishings.

I would imagine that the sellers would agree to a contingency in which the transaction would depend on the success of this treatment, to be determined several days after the treatment. While this instance with the curry seems pretty specific, it's applicable to some other odors as well, but not if a quantity of material is embedded in a surface, like, say, cat urine.

IMPORTANT NOTE: It cannot be emphasized too strongly that ozone is a potent irritant, and 'consumer' ozone generators, meant to be used in an occupied space, are a bad idea according to EPA and the American Lung Association.

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Mold on Down Coats
Q: What I should I do with my winter down coats that were in a closet that has mold. I only saw a strip on the coat about a quarter inch wide and three inches long but I know that there could be mold that is not seen. Should I put them in the dryer for 15 minutes, air them out, wash them?  I don't think I should have them dry cleaned as that would expose others. 

A: For extensive mold, the coats may not be salvageable. If the mold isn't too bad, I would suggest dry cleaning. I doubt there would be much health risk to others, but what you might do is remove the visible mold using hydrogen peroxide or rubbing alcohol (test on an inconspicuous surface first.) Be aware that killing mold does not inactivate harmful products. (You might also try using soap & water to remove the mold.)

If the closet is on an outside wall, it likely gets cold during winter, with humidity levels high enough to support mold growth. Leaving the door open a bit, or installing louvers in the door (top & bottom) should allow warming that may prevent this. You could also leave a closet light on, but make sure that it is at least a foot away from flammable materials. 

PS...It wouldn't hurt to first try the dryer after removing visible mold. If there is still a smell,then try the dry cleaning. If the smell persists, then you will probably have to discard the coat, as the mold is probably in the down.

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FOR IMMEDIATE RELEASE: Buying A Space Heater: Consumers Beware! 
As we deal with the cold weather, and worry about dramatically higher heating costs, many of us seek ways to reduce our winter heating bill. One such method is to turn down the thermostat and use space heaters to warm the room we are in. Electric space heaters are a popular choice, in part because electricity costs are not predicted to increase as much as other fuels. Another advantage is that local heating in a chilly room is less expensive than turning up the thermostat. Many types of electric space heaters are available. One important reality that buyers should be aware of, however, is heater efficiency.

Unlike many things in life, the process of converting electricity into heat is 100% efficient. This is true for both expensive and inexpensive heaters, and is based on simple laws of physics. While there are different advantages and disadvantages to the various types of heaters, consumers should not be misled by any claims of spectacular performance. An electric space heater operating at 1500 Watts will produce exactly 5119 BTU’s (a measure of heat) each hour, rain or shine, no matter what.

According to Joseph Ponessa, Professor Emeritus of Housing at Rutgers Cooperative Extension, buyers of space heaters should beware of excessive claims. Can a space heater produce more heat than other space heaters? Only if it uses more energy. Remember that all electric space heaters, no exceptions, are 100% efficient. Can a space heater cut your energy bills in half? Probably not. The biggest portable space heaters produce about 5000 BTU’s per hour. The furnace in an average-sized house produces about 100,000 BTU’s per hour. So while a space heater may make one room comfortable, dollar savings will be limited. Beware of shutting off the heat to unused parts of the house. This runs the risk of freezing some pipes. What about a “new scientific breakthrough” or “space-age technology”? No luck here: no matter what, you will always get 3412 BTU’s for every kilowatt hour used. No more, no less. If the heater contains a special metal or a special oil to hold the heat, it will be released more slowly, over a longer period of time. This may enhance comfort. But it will be the exact amount of heat that is provided by the electricity consumed. No “special” materials will provide more heat for the electricity consumed.

What kinds of space heaters are there? There are two general classes of space heaters: fuel-burning (kerosene or gas-fired) and electric. Fuel burning heaters may be vented or unvented. While the unvented heaters put more heat into the house, they produce indoor pollution, lots of moisture and a fire risk as well.

Electric heaters are generally less risky, although it is extremely important to follow manufacturer’s instructions for all space heaters. Since electric space heaters consume a lot of energy, they should be used only on electrical circuits that do not have other major appliances (refrigerators, toasters, etc.) connected to them. If fuses regularly blow, or circuit breakers trip, try using another outlet. Remember, most of the electric circuits supplying wall outlets in your home are rated at 1800 or 2,400 watts. Therefore, an electric space heater operating at 1500 watts is using more than half the rated capacity of its circuit. Don’t use an extension cord with an electric space heater. This may risk a fire.

There are several types of electric space heaters. One type produces warm air. This is known as a convection heater. The other type, a radiant heater, mainly warms nearby objects and may provide more comfort in some cases. Radiant heaters have a quartz tube that gets hot and mainly produces heat rays (infrared energy). Some convection heaters have a metal element that glows red and can be a burn or fire hazard. Other convection heaters look like a radiator or baseboard heater and are filled with oil. These operate at low temperatures and don’t get hot enough to cause burns or fire.

There are many different space heaters on the market. Choices depend mainly on convenience, appearance and features, such as low-medium-high settings. For the latest advice on heater selection, consult consumer publications such as Consumer Reports.

Prepared by:
Joseph Ponessa, Ph.D.
Extension Specialist and Professor Emeritus
Housing, Indoor Environments and Health
Rutgers Cooperative Extension

Download this press release in PDF format here.

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Testing for Mold 
Q: I am 65 years old  and have had asthma for the last 20 years! I go to a pulmonologist maybe four times a year and they never seem to find out what's causing me to cough, choke and wheeze, I use asthma medication all year and for some unknown reason I get this upper respiratory infection, post nasal drip, etc. in January and February when my heat is on. I saw a program on Discovery Health last night and this lady had my same symptoms and they found MOLD in her house, hidden behind the walls and under the sink: she was told to never go back in there and in three months she recovered. I need some help in testing and cleaning mold, if I have it, in my home.  Where can I go? I have had my ducts cleaned, but didn't see any difference. HELP.

A: Your question is a difficult one to answer. The most important thing to know is that the symptoms that you describe are common to a wide variety on indoor pollutants including mold. (By the way, some mold spores are everywhere, indoors and out, all the time.) While some people are especially sensitive to mold, problems usually arise when there is a moisture problem causing large colonies of indoor mold to develop. When this is the case, it is often possible to see, or be aware of the moisture issue; and most people experience the moldy smell when entering the problem area. So unless you (or others) experience a mold smell when entering your home, there probably is not a problem.

Moisture problems can be more difficult to identify. There are many causes (rain, plumbing leaks, and excess moisture). A few important ones include gutters that overflow, or low spots near the home, depositing rainwater near the foundation-both leading to damp basements & possibly wet walls. Unvented gas or kerosene space heaters (and clothes dryers) also produce lots of moisture.

Hiring someone to test the home is also difficult. While there are many reputable firms, some others are not really qualified, and in NJ there is no state licensing or certification. Other firms may recommend expensive work that is not needed. Expect to pay $500 or so for properly done mold testing. Because mold is everywhere, any testing will show the presence of mold, and dishonest testers can scare you with results that are simply normal indoor concentrations. If you are in NJ, the Department of Health & Senior Services has a listing of inspection firms meeting minimum qualifications.

If you wish to have the home tested, consider overall environmental evaluation of the indoor environment rather than focusing just on mold. This should involve a walkthrough by an inspector, and perhaps a few tests depending on the findings of the walkthrough. But before you do this, I would strongly recommend learning as much as you can about indoor pollutants, so you are a knowledgeable consumer when hiring the inspector. There is lots of info at www.healthyindoorair.org. In particular, look for the “Indoor Air Hazards" booklet. Lots of info is also available on the EPA website. Finally, your doctor may be able to offer some help. Nearly all asthma patients can lead normal lives, but successful treatment involves 1) working with your doctor to find the best medication plan for you; and 2) your efforts to find and avoid the things that trigger your asthma episodes (which is what you are trying to do now.)

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Getting Rid of Roach Smell 
Q: I would appreciate some suggestions on how I can get rid of the roach smell in a 16 ft. mobile home I bought.  It was infested with roaches when I bought it. They were all over it, including inside the appliances. We thoroughly cleaned the mobile home, washing all the walls and cabinets and even ripped out the carpet and replaced it with wood floors. We painted the sub-floor & ceiling with some kind of paint to seal out odors.  We took the kitchen cabinets down and cleaned them completely before rehanging them and we replaced all the appliances. The crawl space was cleaned out and there are no signs of dead roaches any longer. The problem is when the house is closed up the roach smell returns. The county agent suggested there could be remnants of roaches in the walls, but I don't think so. Any suggestions?  And yes, we are now wondering why they didn't just buy a new mobile home to place on that lake lot.

A: My generic suggestion for such odors is to treat them as smoke odor after a fire: call a Fire/Water/Smoke damage remediation firm. They will set up a commercial ozone generator (and perhaps other measures) to destroy the odors. NOTE: A) this is done in an UNOCCUPIED building; B) Occupants should be strongly discouraged from do-it-yourself measures using consumer air cleaners/ozone machines in occupied spaces since even the lower levels from these machines can be harmful to health according to the EPA and American Lung Association. Also, the space should be thoroughly aired out before re-occupancy. 
Occupants should also check inside of electrical outlet and switch boxes after first turning off the electricity. These are warm locations sometimes favored by roaches.

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Lead Pipes 
Q: I live in a rented 1974 mobile home and recently had to have some plumbing fixed. I noticed that the water pipes on the house are made of a silver colored metal. I am wondering if they may be lead pipes and what, if any, health concerns I should be aware of.

A: I would be very surprised if pipes on a 1970’s vintage trailer were lead. Most likely, they are copper and usually, where readily visible (such as supply lines to toilets), chrome plated brass. Steel is a remote possibility, and easily verified with a magnet, which would not be attracted to brass, copper or lead.

You might be able to tell whether the pipes are copper or lead by looking at some concealed pipe; often, pipes are visible behind an access panel for a tub or shower, or beneath a sink. Rub the pipe with some steel wool to get rid of the tarnish. Copper will eventually reveal a copper color, like a penny, while lead will remain grey or may develop a silvery shine as you continue to polish.

If you are still concerned, you can have the water tested and I would expect that testing would be accurate. Unless you have a private well, or a very small water supplier serving a small number of users, federal regs require that the supplier test water for contaminants, including lead, once a year. The supplier should be able to provide recent test results for ‘first draw” (taken from the tap before usage in the morning) and flushed samples. As a general precaution, since most faucets contain small amounts of lead, when water has not been drawn from a tap in six or more hours, (first thing in the morning) let it run until it gets cold & never use first draw (or water from the hot tap) to mix baby formula.

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Sweating Windows 
Q: In the morning my window sills are wet and often have black mold on them, but only when the outside temperature drops below 47 degrees. There are no water leaks around the windows or elsewhere in the house. The windows are at least 14 years old and are double paned. I keep the heat around 70-72 and the humidity is 41%. The problem started to occur last year. I have talked to window professionals who say to replace the windows because the seal between the panes has ruptured. Unfortunately I have no funds to do that; I have pulmonary disease, live on a fixed income and have a mortgage on the house. My thought was to lower the temperature indoors, but that presents some health concerns. Any suggestions for low cost solutions?

A: First of all, I would be very suspicious of the 41% humidity reading. While there are some good consumer hygrometers out there, others can be notoriously inaccurate. based on the indoor conditions reported, the dew point for condensation would be 43 deg F, that is, the inner window surface would begin to show condensation at this temperature. Outdoor temps would have to be below 43 degrees for condensation to take place. While windows would perform somewhat better if the seal were intact, I think it is highly unlikely that window replacement would solve the problem. (As for the advice of the window people, remember: If you're a hammer, every problem looks like a nail.)

So I think the problem is excess humidity in the home. The list of "usual suspects" to run through to identify the moisture source is long, but many possible sources should be obvious. Some not-so-obvious sources include: 1) Unvented combustion: While CO poisoning is the main concern when this happens, properly functioning equipment may not produce carbon monoxide in abundance. However, any combustion produces very large quantities of moisture. Unvented space heaters (Kerosene, natural gas or propane); clothes dryers vented into the home; blocked flue pipes/chimneys from furnaces or water heaters-all produce abundant moisture. Other issues such as backdrafting or rusted heat exchangers in furnaces & hot water heaters also add combustion products (including moisture) to the home. 2) Saturated earth near the house, due to recent heavy rainfalls combined with malfunctioning gutters or downspouts, or low spots near the foundation, can also introduce high humidity levels in the home.

While it would be good to accurately measure indoor moisture levels (electronic hygrometers are about $40 at electronics stores) the windows themselves tell us that humidity is too high. What is needed is a survey to identify sources of excessive moisture in the home. You can find a short list of common moisture sources in the EPA’s booklet “A Brief Guide to Mold, Moisture and Your Home”. If no excessive moisture sources are found, it may be that the home is sealed up too tightly, either built too tightly, or aggressively weatherized. In this case, something will need to be done to bring in additional outside air. 

By the way, lowering the temperature in the home would lower air's moisture-carrying capacity, raising RH, and also lower surface temperatures on windows & exterior walls, making condensation more likely; raising indoor temperatures would lessen condensation.

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Odor from Air Conditioning Ducts (Updated 7/27/2011)
Q: What organization(s) can provide consultation and/or services to rid my house of candida (yeast)? I think the stuff is living in the air conditioning system. There's a pervasive smell as of a human yeast infection, but no one in the family has that condition. We first noticed the smell a year ago. It intensifies with the use of AC and diminishes at other times. Now the problem is worse than ever-actually intolerable. We're losing sleep as a result. We've cleaned the house repeatedly, changed AC filters, even sprayed Lysol into the furnace/AC blower. Please advise. By the way, we're very restricted financially, so we'd especially-though not exclusively-appreciate information about low-cost help on this matter.

A: Since you associate the smell with the AC system, the most likely culprit would be the condensate tray beneath the cooling coils of that system. The coil unit is located above or near the furnace, where the return ducts meet with the supply ducts. This part of the system is known as the Plenum. When the warm, moist return air hits the cold coils, condensation occurs and the water falls into the condensate tray. The little tube that drains this tray often gets plugged up, the tray fills with water, and mold colonies form. If you can gain access to view the coils or tray, you should be able to easily confirm mold colonies.

I would think a duct cleaning service would be best equipped to tackle this job, provided that they do it in a safe fashion, without stirring up a lot of mold debris that would contaminate the ducts. (Duct cleaners, though, do not usually get into the plenum area.) Those who service your furnace should also be able to do this work, although they may not be skilled in doing it in clean, safe fashion. You might even be able to do this job yourself, if you are able to get access to the tray. The job must be done in such a way that it does not contaminate workers of the surrounding area and ducts. Take a look at the EPA booklet "Mold Remediation in Schools and Commercial Buildings" for vital information on personal protection for those doing the work.

Update: A colleague (Ted Funk, Cooperative Extension Specialist, University of Illinois, Urbana.) Added these valuable comments:
1. Such odors from AC systems are often described as a ‘dirty sock’ smell. 
2. The offending mold often grows on the coils themselves. 
3. An AC technician would ordinarily be best qualified to clean the coils.

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Asbestos "Popcorn" Ceiling 
Q: Should I be concerned about asbestos when I scape off the popcorn stuff on my ceiling?

A: A quick search on Google confirmed my recollection: Most (but not all) such ceilings (decorative rough texture-"popcorn") from the 1950’s to the early 1980’s contained asbestos. The only way to know is to have a lab analyze a sample. Take a look at this website, which also discusses a testing protocol: http://www.naturalhandyman.com/iip/infpai/popcornoff.html. While I am somewhat reluctant to recommend a website, the protocol for removal of asbestos here is a summary of that developed by the Clean Air Council of Washington State, and should be reliable if carefully followed.

Generally, it is best to not mess with asbestos. If health exposure is a concern, the best recommendation is usually to leave the asbestos alone, provided it is in good condition (not crumbling or water damaged, for example) and not subject to mechanical abuse. If appearance is a concern, a skim coat of drywall mud (this is probably beyond the skill of most non-professionals) might be considered; if the ceiling is not painted, verify that the coating process will not dislodge the texture material.

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Energy Recovery Ventilator
Q: During one of my home visits I encountered a home where the Energy Recovery Ventilator (ERV) had been unplugged. When I asked the home occupant why it had been disconnected, she stated, “My power bill is less when this is not being used.” What might be the consequences (short of a lower power bill) to this home?  Are there potential health effects? I noticed there was a ventilation hose connected from the gas supplied furnace to the ERV and also a hose connected from the ERV to an outside vent.

A: It's hard to diagnose a problem such as this without actually seeing the system in its context, so my response here is somewhat general, based on some assumptions. As you probably know, the Energy Recovery Ventilator (aka Heat Recovery Ventilator or Air-to-Air Heat Exchanger) provides a means of bringing fresh air into the house while exhausting stale house air, doing this in such a way that saves (captures) most of the energy used to heat or cool that air. (The duct to the furnace goes, I hope, to the return duct).

I like these devices, but their usefulness is decreased in leaky buildings. So even though there is a cost to run the fan, to the extent that this appliance reduces air leakage there is an energy saving on the heating (and cooling) bill. (These devices typically recover 70-80% of the energy in the air that is exhausted.) If the unit is unplugged during mild weather, and windows are opened, there is no adverse effect. The impact of pulling the plug during the heating season would depend on how tightly built the house is. For a very tight house, these units become pretty important; we do need some fresh air for a variety of reasons, mainly pollutant control and moisture control. During the heating season, signs of a too-tight house include condensation on cold surfaces-usually windows-even at moderate temperatures, say in the 40's, but this also depends on the amount of moisture being generated in that particular home. Another sign is cooking odors lingering for a long time-more than a couple of hours. On the other hand, wintertime static electricity indicates a too-dry interior, and probably too much ventilation. 

Ultimately, exposure to high levels of indoor pollutants will make the home less healthy than it would otherwise be. The tighter the house is, the more harm is likely. On balance, these devices represent a good way of providing needed ventilation with minimal energy losses-better than cracking a window open and better than via air leakage. Any information from or about the builder would be helpful: was this built as a high performance building? Or was the ERV installed to fix a problem? If so, disabling it would be a bad idea. (Even more so if someone has blocked off one or both of the hoses/vents.)

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Follow-up Comments Regarding Use of Bleach to Kill Mold
I'd like to provide some additional info on the usage of bleach; my response to last week's question involved a very narrow issue and I think it is appropriate to discuss this in a wider context, especially since some groups oppose the use of bleach under all circumstances.

This is a somewhat difficult question: to use, or not to use bleach. My opinion is that, while bleach (from the jug) is a pretty potent material that deserves a great deal of respect (i.e. Follow The Directions! Always! Really!) it can be safely used in the appropriate circumstances/rules. Bleach can cause burns to eyes, mucous membranes and other sensitive tissues, and can cause asthma attacks in susceptible persons. While I'm aware that some environmental groups discourage bleach use, I did not find such prohibitions in a quick scan of the websites of the American Lung Association, the EPA or WebMD.

From above: The appropriate circumstances/rules for bleach use include:
1. People with asthma or sensitivities to bleach should not use it, and should not be around when it is used.
2. It should not be used around groups of kids, since some might be vulnerable to it.
3. Label directions must be carefully followed-adequate ventilation, dilution and usage according to directions; NEVER use straight bleach. (Dilute bleach may take a few minutes to work, but it's definitely worth waiting.) Dilute as directed-No Cheating!
4. Don't mix with other products: Ammonia, and products containing ammonia compounds, react with bleach to produce a deadly gas similar to the nerve gas used in WW I.
5. Keep bleach containers away from children when it is stored and during use.

With regard to when to use bleach (and when not to) - this is important too. Bleach has two uses- it bleaches/whitens things, removing stains; and it kills germs, mold and other things. BUT, there is a VERY big exception regarding mold-see below.

My response last week involved a question about removing mold stains from household items, and I listed some alternatives for items that bleach might damage. In fact, it might have been better for me to have recommended using the weaker products (rubbing alcohol or hydrogen peroxide) first. For laundering, non-chlorine "oxy" type bleaches are available. 

The MOST IMPORTANT THING to understand about bleach and mold, according to the EPA and others is that for large, thick mold infestations-a few square feet or more-bleach is NOT the way to go. Killing the mold is NOT the right approach, since killed mold spores and debris does not inactivate its harmful properties. The mold should be safely removed (using soap & water) and the moisture problem fixed.

Other situations where dilute bleach (sodium hypochlorite) is used for its sterilization property include swimming pools, water  wells that have become contaminated, and recovery from "blackwater" flooding after the safe removal of mud, mold and other debris. Blackwater flooding refers to floodwaters that have been contaminated by sewage or floodwaters. This flooding, and all groundwaters are considered to carry silt and harmful organisms, requiring cleaned surfaces to be sterilized as well.  

(Please be aware that while 'germ killing' is very important in some specific situations-the above mentioned, along with food prep and in consideration of persons with medical vulnerabilities-we as humans are not designed to live in a sterile environment, and have survived since the beginning of time in the presence of microorganisms. In fact, some research indicates that exposure to microorganisms early in life is important for normal development of our immune system which fights infection.)  

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Using Hydrogen Peroxide to Kill Mold
Q: Will hydrogen peroxide kill mold? If so, why isn't it recommended instead of bleach?

A: Hydrogen peroxide (H2O2) is an alternative for cleaning mold-damaged household items that would be damaged by DILUTE bleach. (Another alternative is rubbing alcohol.) Dilute bleach has always been the "remedy of choice", despite its irritant/toxic qualities, because of its ready availability in most homes; however, hydrogen peroxide is available at almost any drug store and it is inexpensive.

Bleach is probably more effective on stains than hydrogen peroxide, and hydrogen peroxide has a definite shelf life, losing potency in about a year. The two issues here are cosmetic damage and stain removal. An inconspicuous surface should be tested first and if bleach damages the surface, hydrogen peroxide will be a suitable alternative.

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Testing for IAQ
Q: Can someone test the air in my home?

A: If you believe that you have an indoor air quality problem, the right way to diagnose it is to have an on-site evaluation by a knowledgeable person who would walk through the house and, based on observations and knowledge MIGHT recommend one or a few confirmatory tests. As an alternative, if you suspect a particular pollutant is causing a problem - formaldehyde, for example, a formaldehyde test can be done to confirm or disprove this suspicion.

There is, however, no practical way to collect an air sample and, in the absence of on-site inspection, tell what is wrong with the air. Testing must be guided by informed judgments of what the problem might be.

Due to the possibility of unqualified individuals attempting to profit upon concerns about the indoor environment and health, it is
especially important to be a good consumer when hiring someone to do an investigation of the indoor environment. Ask questions: How many building investigations have they done, how do they go about inspecting a building, can they provide recent references, what courses/trainings have they taken? Your local health department may be able to provide a list of contractors doing this type of work. Being a knowledgeable consumer also means learning about indoor pollutants yourself; The EPA has valuable information on their website (www.epa.gov/iaq) or call 1-800-4318. Their booklet “Care for Your Air. A Guide to Indoor Air Quality” is a good starting point.

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Condensation in Crawl Space 
 I live in a hot/humid climate and I have a problem with mold/mildew on the floor joists in the crawlspace of my house. The ducts underneath the house are insulated on the outside but they are dripping water. It's a vented crawlspace with the vents open around the house. Unvented crawlspaces are not always an option here in Alabama with high annual rainfalls and often high water tables. It's a house built in 2002 and I've even attempted installing a suction fan to take the humidity out of the crawlspace. 

A: First, here are some questions to ask if you haven't already: 1) Did you use mastic or appropriate foil-based (backed) tape to seal duct seams before they insulated? This could be one issue. 2) How much insulation is on the ducts? Is it adequate? 3) Do you have a dirt or concrete  floor? If it is dirt, is it covered with a 6 ml or heavier plastic? Or is there too much water to do that? 
4) Are the spaces between floor joist also insulated? Have you checked for penetrations into the crawl space from the flooring etc. above? 5) Have you checked the exterior soil slope and for low spots near the foundation? Are your gutters & downspout extenders etc. moving water well away from the foundation?

If the gutters & downspouts and grading around the building have been attended to, and liquid water still collects in the crawl space, consider groundwater and a high water table. If this is an issue, a sump pump may be needed.

Despite what codes may call for in terms of crawl space ventilation, if crawl space temps are lower than outdoor temps, hot humid summer air may be reaching its dew point in the crawl space, in effect adding more moisture. So you may want to check crawlspace temperatures. (Also, electronic hygrometers, costing about $40 at electronics stores, can provide moisture level readings.). Anyone deciding to experiment with closing off the vents during hot, humid weather should check the crawlspace regularly to ensure that things have not gotten worse. Based on some research findings, cutting-edge building science frequently recommends sealed crawlspaces in hot humid climates, often using a dehumidifier in that space. If you decide to explore this route, be sure to get local expert guidance since this type of approach can be more complicated than one might imagine.

For more help, most of the information in my fact sheet,  When to Ventilate the Basement to Reduce Moisture Problems (FS258), at http://www.rce.rutgers.edu/pubs/publication.asp?pid=FS258

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More FEMA Trailer Information
Q: Please tell me what the risk reduction message to a family who is living in a FEMA trailer that was given to the occupants from left-over stock from hurricane Katrina. The home owner was informed that there was known formaldehyde products in the trailer. Are there risk reduction measures that the family can take? If so, what would that be?

A: I’m not sure  that there are practical risk reduction measures if the trailer is contaminated with Formaldehyde. Here are a few basics; Biggest offenders are “MDF” (medium density fiberboard) used in countertops, cabinets and ‘ready- to- assemble’ furniture. Veneer coverings, & plastic laminates can block formaldehyde release, but beware of uncoated surfaces (inside, underneath counters, etc.) Application of one or more coats of paint or varnish can help to block release here. Releases are maximized by heat & humidity, and lowest under cool, dry conditions. Hardwood plywood paneling is another source of formaldehyde. These products contain substantial amounts of urea-formaldehyde resin, used to bind wood the particles together.

I think the first thing to do is to see if a formaldehyde measurement can be made, to verify the amount of formaldehyde present. The local health department may be able to help here. (Do-it-yourself kits are also Available for about $40.) The background here is that several years after the trailers were first occupied, and after numerous complaints, FEMA removed residents from these trailers. (I don’t know if every FEMA trailer was affected with formaldehyde). Subsequently, the trailers were given away or sold, with the stipulation that they were not to be used for continuous human occupancy. Such notice was affixed to the trailer, as I recall, and was not to be removed. In addition to its characteristic smell, Formaldehyde causes irritation of the eyes, nose & throat, along with irritation & coughing. Note that these symptoms are common to many other irritant pollutants.

If there are high formaldehyde levels, the process of coating bare surfaces of pressed wood products would involve considerable work. Since elevated formaldehyde poses acute and long term health risks, alternate living arrangements should be considered if at all possible.

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Carpet Bleaching in High Traffic Areas
Q: I am on the Board of Directors (Treasurer) at the (apartment building name & location redacted). About three years ago, we had (brand name redacted) carpeting installed on 10 of our 12 floors. A year and a half later, the carpet began to fade, especially in heavy traffic areas. (Brand name redacted) sent a mill inspections service out to look at the carpet and the result of their inspection was this: The pile surface displays a faded orange-ish hue around the elevator and front portions of each hall on most floors. The condition is visible on the carpet base in the same areas and is related to Fume Fading, a topical attack on the dye from atmospheric conditions. The report goes on to say that: the greatest concentrations around elevators doors, trash doors and stairway doors leads us to conclude the source of the contaminant is coming from the lower portion of the building and that the elevator shafts and trash chute act as chimney transports in distributing the affecting contaminants through the building. We need help determining whether this report is accurate. (Brand name redacted) is unwilling to honor their warranty with us and we may be left with the expense of replacing the carpet. If our building is contaminated, we need to have it tested. Please advise me on how I should go about arranging for the testing. Hopefully, you can steer me in the right direction.

A: There are two issues here: One involves air flows: are there excessive air flows from the elevator shafts and stairwells? This is a possibility especially if there are mechanical ventilation systems in operation. A pressure imbalance can direct airflows in the building, sometimes in opposite directions to what one might predict on the basis of 'passive' principles- warm air rising, cool air settling to lower levels. A chemical "smoke pencil", used by energy auditors and others, can qualitatively demonstrate air flows. Differential and comparative pressure measurements, comparing pressures in the various shafts to pressures on individual floors, can quantify such differences and point out anomalies that might, for example, transfer bulk air (and pollutants) from one area to a distant location. (From the basement, for example, to the 5th and 7th floors if pressures on these floors are lower than other levels.) Of course, the elevators themselves act as pistons in their shafts, pushing and sucking volumes of air as they travel.

The other issue involves the presence of volatile pollutants that might bleach the carpet. Bleach fumes (from a laundry operation) and ozone (from large electric motors or other sources) come to mind. Perhaps the carpet manufacturer can suggest other possible volatiles that affect their carpet. Are there any such sources on the premises, or commercial operations in the building? Are there fresh air intakes that are close to outside pollution sources?

While a building scientist/ investigator could do some of these diagnostics, they could also be done by a capable HVAC contractor or a good energy auditor who understands building airflow dynamics and is equipped to do pressure measurements. Analysis for the offending pollutants would have to begin with a list of suspects based on potential bleaching agents linked to possible sources in the building.

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Reduction of Formaldehyde in FEMA Trailers
NOTE: Media reports in 2009 and 2010 cited high levels of formaldehyde in “Katrina Trailers”, temporary housing units that had been hurriedly constructed by FEMA to house displaced residents whose homes had been destroyed by hurricane Katrina.
One question below concerned the use of elevated temperatures in affected units to ‘bake out’ the formaldehyde. (This is a practice sometimes used in new buildings to reduce the levels of volatile indoor pollutants.) A subsequent question asked about the effectiveness of high ventilation rates.

Q: Several years ago, I read an article on "baking" an office building to get all the toxic fumes out. As memory serves, the office was vacant, the heat was turned up to about 90 degrees for a period of time and then the office was aggressively ventilated and then the procedure was repeated. This was to remove or reduce the fumes from the carpet and furniture. Maybe this could be a possibility to make these trailers useful and not harmful?

A: I don't think this would work for formaldehyde in trailers. Bake out affects volatiles that are more or less readily accessible to ventilation. It may help with traces of formaldehyde in, for example, fabric (drapes); but the bulk of this gas in the trailers (and many other problem applications) is likely in pressed board products such as MDF (fiberboard). Here, formaldehyde can represent a substantial constituent of the product, in the form of urea-formaldehyde (UF) resin, used to bind the wood fibers together. (Other binders are available, but it seems likely that many of the Katrina trailers used the UF materials.) MDF is typically used as sheathing and in the construction of cabinets and countertops. Paneling and some plywoods also use UF resins. The UF resin can break down in the presence of moisture, releasing formaldehyde, and the process accelerates as temperatures rise. Because of the amount of UF involved, and the fact that UF is embedded throughout the depth of the product, offgasing of formaldehyde from MDF typically progresses for long periods of time - years, in some cases. It is unlikely that a bake out would mitigate the long-term problem. Formaldehyde release can be controlled by plastic veneers or some types of coatings.

Q: Do you think the trailers could be ventilated with mechanical ventilation that would lower exposure enough? Although the trailers have higher levels than homes, I understand that the recent California study found formaldehyde (among other air toxins) in newer homes and the state is moving towards requiring fresh air make-up in home ventilation systems.

A: It's hard to say if ventilation would solve the problem (and a positive answer may be moot vs the PR/emotional aspect of this). And given the energy penalty of ventilation, such a strategy would not be practical. Moreover, these trailers are probably not especially well built, and likely have excessive ventilation already.

Another whammy for trailers is the simple geometry of small buildings: there is a relatively large ratio of surface area to volume in smaller enclosures. (For a cube, surface area increases as the square of the side dimension, while volume increases as the cube of that dimension; so smaller structures have a relatively larger area compared to their volume, a disadvantage if the surface area is comprised of a pollutant source.)

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Mold Stains on Siding
 I have a putty colored mold growing on the aluminum siding and wood columns of my home. It is in an area that received morning sun and afternoon shade. The mold is like the slime molds that grow on mulch, but it's only on the house. I cleaned it off with a bleach and water solution (the solution was about 50% bleach). Three to five days after washing it off it reappeared. It's Georgia so it has been humid outside. Any suggestions of how to resolve the problem?

A: You might try another washing, using a dilute bleach solution (1 cup per bucket of water) plus some detergent (adding a half cup of Spic & Span or Soilax...or TSP substitute), and letting it stand for 10 minutes or so before rinsing. The wait time is important. But if the original bleach wash didn't work, I'm not so sure that this will; but again, it couldn't hurt to try this on a small test area.

Ultimately, you may need to repaint. If so, the paint should have a mildewicide additive (usually purchased separately). It would be worthwhile, however, to get some technical advice from the paint manufacturer. There are specially formulated paints for siding, but there may also be a 'Best' recommendation for a paint or primer especially recommended for mildew resistance.

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Sewage Smell in Basement
Q: Our sewer was worked on this summer and post completion, we noticed a sewage smell in our basement. A technician came to our house and recommended we put bleach down the drain to take away the smell. I contacted a supervisor and here is the response. I mainly want to know whether the recommendation of bleach is sound, and if not, I'd like to provide them with alternative, research-based information, so other families are not given the same response. Here is the email I received:

After we received the e-mails below, we started our investigation as to what could possibly be the cause of the sewer smell coming from your basement drain. Our contractor sent a camera down the new lateral that we installed and there are no issues and it is free flowing. The only thing that we can surmise is since your sewer lateral is connected to a 15-inch sewer main, which is a larger sized sewer main, when there is heavy flow in the main that’s when you will tend to notice the smell. Now you’re obviously asking yourself why didn’t I have this problem before the company separated your lateral from your neighbors. We
can only speculate why this could be happening. Under your old connection, there was a 6-inch connection with a “Y” at the property line to serve both you and your neighbor. Over time, roots and other build up starts to impede flow from your houses to the main, but in turn it also could act as a buffer not allowing the sewage smell from reaching your house. When the sewer lateral was separated and individual 4-inch connections were installed, this provided both you and your neighbor with brand new, unimpeded sewer connections. As previously stated, due to your connection flowing into an existing 15-inch sewer main, the high volume of sewage flowing through the mainline in the street could be the cause of the smell. As previously stated, this is only speculation since there are no visual issues with the newly installed sewer lateral. The original representative that came to your house suggested that you pour bleach down your drain to help eliminate the smell. We would suggest the same. If you
continue to have the same issues, it is possible that there could be issues with the sewer connection on your property, to which you would have to hire a plumber to investigate accordingly.

A: One's first inclination is to think that the technician that investigated the new line included an expert check of the piping in the immediate vicinity of the inspection point. This may not have been the case. Moreover, it is hard to imagine that pouring bleach down a drain could do any more than replace the sewer odor with a bleach odor. And I can't imagine how this would provide anything more than a very short term solution.

Ordinarily, sewer odors are blocked from the building by a water-filled trap (that U-shaped drain that you see below the sink) on/near drained plumbing fixtures. The trap retains water that blocks sewer gases from entering the building. In investigating sewer odors, the first thing to look for is an empty trap. This can be done simply with a flashlight in some traps; If the trap can't be directly visualized from above, it may be possible to ID an empty trap simply by a strong smell coming from a particular drain. Or you could plug up a suspect drain & see if that improves things. Likely causes of a dry trap are: evaporation from a seldom-used drain (such as a floor drain) or siphoning, when a large discharge of drainwater (from a washing machine or toilet) sucks the water from a nearby trap because that trap is not properly vented. This would need to be corrected by installing a vent. (You can prevent the floor drain from drying out by pouring a couple of ounces of mineral oil into the drain.) The pipe-root theory may be correct, but I would start by looking for an empty trap.

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Yellowish Stains on Bathtub
 I need some of your expertise on what causes yellowish stains to appear on a cast iron bathtub after I cleaned it with a cleaner that contained bleach. The stains appeared to be in the areas where the tub had small scratches. I wondered if it could be a reaction of the bleach with the cast iron. I'd like to know how to remove the stains and how to clean the tub in a manner that won't result in the same problem. 

 It sounds like iron chloride.  The same thing happens in laundry, if you use chlorine bleach in water that has a high level of iron you get brown stains on white clothing items.  I would advise you to use a cleaner without chlorine bleach; look for a product that removes lime & iron stains from porcelain fixtures. I’ve had good results with “Tub 'n Sink Jelly”. (Apologies for mentioning a brand name; I don’t know of any other similar products.)

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Moisture Readings After Flood
 I have recently had a clean water flood in my home and in the course of drying it, I cannot find any good data on terminal moisture readings.  That is, how low should moisture meter readings be in order to deem the remediation process successful and begin restoration.  The drying company engaged by my homeowners insurance carrier packed up and left after four days, but I'm still getting moisture meter readings in excess of 22-24% behind sheetrock at the sill plates.  The house is slab-built. 

I'm also curious about the appropriate protocol for taking moisture meter readings.  If the surface of a 2 x 6 appears dry, but an internal reading shows a 24% moisture content, is it OK to begin restoration?

A: I assume that you’re taking readings of moisture content with a moisture meter; as I recall, wood at moisture content above about 16% is susceptible to mild growth, although the progress of growth is temperature dependent. If the sheetrock itself is reading 22%, this sounds quite high and I believe there is a serious possibility of mold growth. (Citation: Lstiburek, J. Moisture Control for Buildings. ASHRAE Journal. Feb. 2002. pp 36-41.)

The general recommendation of the Institute of Inspection, Cleaning and Restoration (IICRC, a trade association that sets standards for water damage remediation) is that flooded materials need to be dried out within 48 hours before mold growth gets out of control, although this criterion may be stretched a bit in cooler temperatures. Generally, it is only possible to salvage drywall that has been slightly wetted, but saturated drywall is usually cut out (in increments of 2 feet) to a point above the line of flooding, and replaced after the framing has dried. A good reference on mold cleanup is EPA’s “Mold Remediation in Schools and Commercial Buildings”.

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