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Federal Government Recommendations
     -OSHA (Occupational Safety & Health Administration)
     -EPA IAQ (Environmental Protection Agency: Indoor Air Quality)
     -EPA  Table 2 (Environmental Protection Agency: Table 2 Guidelines)
     -NIOSH (National Institute of Occupational Safety & Health)
     -CDC (Centers for Disease Control) 
     -Sampling for Mold

North Respirators for Mold Remediation



Sampling for Mold
Currently there are no Federal Standards or recommendations (e.g. OSHA, NIOSH, EPA) for minimum exposure to airborne fungi (molds) and their spores. Measurements of airborne concentrations can be performed, but it is costly and needs to be evaluated by someone experienced in microbial investigations. Without a Permissible Exposure Limit (PEL) or Threshold Limit Value (TLV) set by OSHA, NIOSH or the EPA the results of any air sampling would have limited use. Visible evidence of mold is enough cause to remediate the area.
 Stachybotrys spores attached to a hyphal fragment. Presence of this type of structure and/or hyphal fragments in an air sample is a good indication of mold sources in the area. Photo provided by WonderMakers Environmental, Inc. of Kalamazoo, Mich.

OSHA: A Brief Guide to Mold in the Workplace
In most cases, if visible mold growth is present, sampling is unnecessary. Air sampling for mold may not be part of a routine assessment because decisions about appropriate remediation strategies often can be made on the basis of a visual inspection.

Mold growth on windowsill. Photos provided by Envirotech Clean Air, Inc. of Stoneham, Mass.

Your first step should be to inspect for any evidence of water damage and visible mold growth. Testing for mold is expensive, and there should be a clear reason for doing so. In many cases, it is not economically practical or useful to test for mold growth on surfaces or for airborne spores in the building. In addition, there are no standards for “acceptable” levels of mold in buildings, and the lack of a definitive correlation between exposure levels and health effects makes interpreting the data difficult, if not impossible.

Testing is usually done to compare the levels and types of mold spores found inside the building with those found outside of the building or for comparison with another location in the building. In addition, air sampling may provide tangible evidence supporting a hypothesis that investigators have formulated. For example, air sampling may show a higher concentration of the same species of mold when the HVAC is operating than when it has been turned off. This finding may convince the investigators that the mold is growing within, and being disseminated by, the HVAC system. Conversely, negative results may persuade investigators to abandon this hypothesis and to consider other sources of mold growth or dissemination. If you know you have a mold problem, it is more important to spend time and resources removing the mold and solving the moisture problem that causes the moldy conditions than to undertake extensive testing for the type and quantity of mold.

 Mold growth in return air plenum under vertical air handler. Photo provided by Envirochex of Dallas, TX.

If you are in doubt about sampling, consult an industrial hygienist or other environmental health or safety professional with experience in microbial investigations to help you decide if sampling for mold is necessary or useful, and to identify persons who can conduct any necessary sampling. Due to the wide difference in individual susceptibility to mold contamination, sampling results sampling may have limited application. However, sampling results can be used as a guide to determine the extent of an infestation and the effectiveness of the cleanup. Their interpretation is best left to the industrial hygienist or other environmental health or safety professional.

Sampling for mold should be conducted by professionals with specific experience in designing mold-sampling protocols, sampling methods for microbial contaminants, and interpretation of results. For additional information on air sampling, refer to the American Conference of Governmental Industrial Hygienists’ document, “Bioaerosols: Assessment and Control.” In addition, sampling and analysis should follow any other methods recommended by either OSHA, NIOSH, EPA, the American Industrial Hygiene Association, or other recognized professional guidelines. Types of samples can include: air samples, surface samples, bulk samples, and water samples from condensate drain pans or cooling towers.

Microscopic identification of the spores/ colonies requires considerable expertise. These services are not routinely available from commercial laboratories. Documented quality control in the laboratories used for analysis of the bulk, surface, and other air samples is necessary. The American Industrial Hygiene Association offers accreditation to microbial laboratories (Environmental Microbiology Laboratory Accreditation Program (EMLAP)). Accredited laboratories must participate in quarterly proficiency testing (Environmental Microbiology Proficiency Analytical Testing Program (EMPAT)). 
Source:  OSHA: “A Brief Guide to Mold in the Workplace”



Standards or Threshold Limit Values (TLVs) for airborne concentrations of mold, or mold spores, have not been set. Currently, there are no EPA regulations or standards for airborne mold contaminants.


Large Buildings and Mold
EPA has a number of resources available, you can start with the Indoor Air Quality Building Evaluation and Assessment Model (I-BEAM).  I-BEAM updates and expands EPA's existing Building Air Quality guidance and is designed to be comprehensive state-of-the-art guidance for managing IAQ in commercial buildings.  This guidance was designed to be used by building professionals and others interested in indoor air quality in commercial buildings. I-BEAM contains text, animation/visual, and interactive/calculation components that can be used to perform a number of diverse tasks. See

See also "Building Air Quality: A Guide for Building Owners and Facility Managers" and the "Building Air Quality Action Plan" Excerpt from the Building Air Quality: A Guide for Building Owners and Facility Managers, Appendix C - Moisture, Mold and Mildew:


How to Identify the Cause of a Mold and Mildew Problem
Mold and mildew are commonly found on the exterior wall surfaces of corner rooms in heating climate locations.  An exposed corner room is likely to be significantly colder than adjoining rooms, so that it has a higher relative humidity (RH) than other rooms at the same water vapor pressure.  If mold and mildew growth are found in a corner room, then relative humidity next to the room surfaces is above 70%.  However, is the RH above 70% at the surfaces because the room is too cold or because there is too much moisture present (high water vapor pressure)?

The amount of moisture in the room can be estimated by measuring both temperature and RH at the same location and at the same time.  Suppose there are two cases.  In the first case, assume that the RH is 30% and the temperature is 70oF in the middle of the room.  The low RH at that temperature indicates that the water vapor pressure (or absolute humidity) is low.  The high surface RH is probably due to room surfaces that are "too cold."  Temperature is the dominating factor, and control strategies should involve increasing the temperature at cold room surfaces.

In the second case, assume that the RH is 50% and the temperature is 70oF in the middle of the room.  The higher RH at that temperature indicates that the water vapor pressure is high and there is a relatively large amount of moisture in the air.  The high surface RH is probably due to air that is "too moist."  Humidity is the dominating factor, and control strategies should involve decreasing the moisture content of the indoor air.
Source:  EPA: Indoor Air Quality: Mold







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