Sunday, April 30, 2006

Will "Black Mold" Return if Moisture is Kept Low?

Black Mold Question from a Reader:

I have been finding your site very informative, and have a question (actually a statement) but can you confirm if the following is mainly correct?

Black Mold is found everywhere, in nature, outdoors, indoors etc. It isnt until a constant moisture source and humidity conditions are present that the black mold might actually become a problem, forming in colonys, creating problems, toxins etc. And once those conditions are take care of, with due care to avoid cross contamination, and moisture problems are taken care of and humidity levels are under control, the mold can be properly remediated and therefor resolved as long as moisture problems are constantly checked on for further invasion and damage, and things that are installed (ie: C/A etc) to help humidity issues are cleaned properly.

Thank you,

"Black mold" is not the issue

Reply from D.F.

Black mold is not necessarily the issue in a building. Public fear that is focused only on "toxic black mold" is a bit of confusion caused by media attention to the Stachybotrys chartarum scare.

1. Some black molds are perfectly harmless such as black mold found on much new framing lumber and which is in the Ceratocystis/Ophistoma group - a cosmetic only mold which is not harmful to humans and which
does not rot the wood.

2. Black mold, even if a toxic one may not be what is making occupants ill: Some black molds that people fear, such as Stachybotrys chartarum, are not normally airborne and become so only in response to violent disturbance such as during demolition. So even though this mold can be toxic and seems to be associated with a wide range of complaints, the fact that it is seen on a building wall does not assure that this is the mold to which building occupants are being exposed.

3. Visible mold as a moisture indicator: Black mold" in a building thus should be considered an "indicator" mold of wet conditions, and a careful inspection is in order. While S. chartarum is a "black mold" which can be harmful, almost always, when this mold is found in a building, or when other "black molds" are observed (some are not relally black but look so on a surface and outside the microscope), I find other more problematic but harder to see but more airborne molds such as Aspergillus sp. when I inspect thoroughly.

What is important, particularly if people are sick, is to have a building expert, someone who knows where and how to look for problem molds in buildngs, inspect the property to find the leak history, mold reservoirs, and to do enough mold identification to assure that the real problems, if any, have been found and that the scope of cleanup work can be specified.

I emphasize point #3 because in most of the buildings I inspect, where an occupant has become worried about "black mold" someone has seen, the dominant problem molds in the buildings are NOT the "black molds" that were observed but rather harder to see light colored but more-airborne smaller spore and often toxic or pathogenic molds such as those in the Aspergillus sp. group.

I agree that once a building has been established as adequately clean of mold, monitoring leaks and humidity are key.

I agree that if we keep indoor humidity at proper levels and do not permit leaks and moisture problems to go unattended, we would not expect problematic indoor mold growth.

More in-depth discussion of these points can be read at the following articles:

Mold Action Guide - my main "Mold Action Guide" step by step instructions on what to do about mold in buildings

How to Look for Mold

How to prevent mold list of articles

How to Prevent Mold in Buildings main article on this topic

How to Get to Mold-Resistant Level of Indoor Humidity

Responding to Building Leaks and Floods to prevent rapid problem mold growth in buildings.

If you or other blog readers have other content suggestions I'd appreciate hearing from you.

Daniel Friedman

This Blog is about "What to do about mold in buildings"
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 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.