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.

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!

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.

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 athttp://www.rcre.rutgers.edu/pubs/publication.asp?pid=FS257

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.

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: http://entomology.ucr.edu/ebeling/ebel5-2.html 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.

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.

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. 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.
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.

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.

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.
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.)
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.
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.
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.

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.

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.
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.)
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.
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.
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
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.
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.
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.
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.)
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.

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.
A: 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.)

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.


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.)