When is mold a problem in buildings? What should be done about it? Find expert field and lab testing, inspection, remediation advice, but ... avoid "fear of mold" and bogus advice which can both cost you and yet may not really address the problem effectively. My interest is in providing expert service to my clients, protecting not only their health but their wallets. I provide field investigations to find problems and to recommend solutions to mold in buildings, and I operate a forensic laboratory in New York which accepts mold and other indoor air and particle samples for examination. In depth information is at www.inspect-ny.com and the links at that page. Website content suggestions are most welcome.
Case Histories: Here I post summaries of field and lab toxic or allergenic mold and other indoor air quality investigations. I omit private information. I describe observations, procedures, and findings helpful to readers who are trying to remedy their own mold, allergenic, carbon monoxide, odor, or other indoor air and related health concerns in their indoor environment.
Client asks about indoor mildew, strange wall blisters, and what mold to test for
First off thanks for your very detailed website. I have a question about what to sample for a mold analysis. We are renting a home a home where there is what appears to be visible mold on some of the interior surfaces of exterior walls. I have shown this to the management here; however, they repeatedly minimize/ignore the problem and will not do any testing.
We have explained that my partner has been having health/respiratory problems that we believe might be connected to mold, so we would like to have this identified in order to take care of our health. In turn they simply doused the area with bleach. That was a week ago and it has already started to grow back.
In the meantime, they have claimed that this was simply "surface mildew" and their lawyers have written us a letter to warn us, well, I'm not really sure what it is to warn us, but mostly it seems like an attempt at intimidating us even though they admit it is a common problem in this community. It does however seem like it could be primarily a surface problem as all the walls are bizarely impenetrable--old military housing.
Since it is a rental unit (therefore we can't do bulk sampling) and the mold is visible, we are wanting to do simple tape-lift sampling for identification purposes. Until we get some handle on what we are dealing with we can't really decide how to proceed.
The question that I have for you pertains to an unknown substance. Once we performed the first cleaning of this substance in our closet, which was heavily effected, the substance began appearing in other rooms where it had not been before (the same after they doused it with bleach). After it had spread, I found what appeared to be a simple bump in the paint on one wall. I rubbed a washcloth across it, and the bump was actually a white surfaced, kind of creamy yellow goo (not a scientific term, I apologize)--the best description that I have for it is that it seemed kind of like brie with the white outside and the inside was similar, kind of yellow, soft, etc. Underneath that was the paint. After they did their bleaching, more bumps appeared in the paint in other areas of the house, as though there were something liquid under them. (They are soft and squishy.) As I said I am no expert in mold, therefore I am not sure if this sounds like it could be connected to you. Does it sound like something that we should tested, and if so what is the best way to get that done/get it to you?
Thank you very much for your time and any insight that you can provide -- Dianna, 3/1/2006
Our Response - Sounds like water and bleach behind paint - excessive and improper "surface cleaning" does not correct a problem mold reservoir
1. There is no mildew in buildings. Mildew is an obligate parasite that grows ONLY on living plants - so unless your home is made of grapes or lilac leaves there is no mildew on it. What grows in buildings that looks like mold is mold. Some mold is harmless-cosmetic; some is allergenic; some can be pathogenic or toxic. People who are at extra risk such as with immune disorders or respiratory concerns are at extra risk.
Tips on how to look for mold are at
Tips on how to use your flashlight to spot hard-to-see mold are at
Pictures of what mold looks like in a building are at
Stuff that is not mold but is sometimes mistaken for it is shown at
2. The mold you see might be "surface" mold or it might be the tip of an iceberg of a larger mold reservoir - the distinction depends on why it's growing where it is and where leaks have been throughout the history of the building. If all you see is a small area (less than 30 sq.ft.) it is unlikely to be the principal problem in a building but it might indicate that there is a larger but un-detected problem. My web articles discuss how to look carefully for mold.
3. Sampling - you can't do invasive inspecting like checking wall cavities but you can
- notice evidence of a history of leaks into building cavities - which raises the level of risk of hidden problems
- notice where there is visible mold and collect a few surface samples using tape www.inspect-ny.com/sickhouse/bulksamp.htm has the procedure - sample things that look different by color, texture, or by what they're growing-on (drywall vs. wood for example).
- collect a sample of settled dust from one representative area, perhaps a bedroom, to see if we can pick up unusual levels of problem mold spores in that material - which would indicate that there has been a high airborne mold level at some time.
Instructions for easy and inexpensive tape lift sampling are at
4. Bleach - if building maintainers used bleach as a "mold treatment" that suggests that work is being done by people who lack good information about how to clean up or "remove" problematic mold in a building. The object is to remove problem mold, not to "kill it" since "killed spores" even if you could kill them all (which you can't) may still be allergenic or toxic to the occupants. Further, surface treatments ignore possibly significant hidden mold reservoirs.
Finally, any demoltion or "cleaning" that blows dust all over the apartment or your belongings is at risk of increasing rather than reducing the health risk in the building.
5. Wall blisters? From your description of blisters appearing only after someone bleached and washed the wall surfaces (superficial and perhaps inadequate mold cleanup) I don't know what you've observed or even whether or not it's mold - yellow goo? It sound ass if your observations may be leak or moisture related which in turn are key factors in assessing mold risk. If the walls were treated with strong bleach and water it's possible that that substance has damaged, penetrated, and is causing blisters in the paint. I'd try pricking a blister and collecting the liquid for analysis.
I'd inform the "lawyers" that the cost of making you sick or sicker, or the cost of having to do extra cleaning if the apartment people don't follow proper procedures, or the cost of having to inspect and clean the building repeatedly because they're starting off with shortcuts are all likely to ultimately cost the building owners a lot more than the cost of doing it right the first time.
-- Daniel Friedman 3/1/2006