Indoor air quality is compromised by both biological and non-biological pollutants. Sources of biological pollutants include microorganisms, animal, insects and related organisms.

The most common biological pollutants include molds and their byproducts, dust mites, pet dander (scales from hair, feathers, or skin), droppings and body parts from cockroaches, rodents and other pests or insects, viruses, and bacteria. Due to their small size, many of these biological pollutants are airborne and easily inhaled deep into the lungs.


Health Effects From Biological Pollutants
Some biological pollutants may cause serious health problems including hypersensitivity pneumonitis, allergic rhinitis, and some types of asthma. Other health problems attributed to biological pollutants are sneezing, watery eyes, coughing, shortness of breath, dizziness, lethargy, fever, and digestive problems.

It is believed allergic reactions occur only after repeated exposure to a specific biological allergen. The reaction may occur immediately upon re-exposure or after multiple exposures over time.

Testing for airborne mold spore concentration is achieved by impacting a known volume of air onto a surface coated with sticky material. As the air hits the sticky surface the spores and any other particulates in the air are trapped. In the laboratory the spores are identified under a microscope, categorised into various groups and counted. This method is excellent for estimating how contaminated the air is but it does not tell us what proportion of the counted spores are still viable. If an estimate of the proportion of viable mold spores is needed, then the air has also to be impacted onto some growth agar media. Viable mold spores would then grow on the media and appear as mold colonies, usually referred to as colony forming units (CFU). CFU is not a very accurate way of measuring the viable proportion of airborne mold spores. This is because a single colony can develop from one spore or a group of spores. Secondly, fast growing colonies tend to overgrow slow growing colonies. Also, the agar media used may not support the growth of all categories of viable spores present in the air.

Testing for mold is not difficult. But you need to know not only where to look for it but also which species are toxigenic or allergenic. One also requires to have a clearly defined objective for the testing. If the objective of testing for mold requires that samples be taken, it is important to know what types of samples to take and the limitations or disadvantages of different types of samples. The type of samples to take is determined by the type of data the mold investigator requires. The type of data required, on the other hand, is determined by the objective(s) of the investigation.

There are some mold training courses out there that can provide you with basic skills necessary for mold investigation. You may want to review the Mold Training Course offered by MBL. This unique, comprehensive one-day training course focuses on how to recognize indoor mold, how to develop effective sampling strategies, how to interpret laboratory results and current guidelines on mold remediation. Course dates are found at http://www.moldbacteria.com/training.html.

Is air sampling of mold necessary? Any type of mold sampling whether air or surface sampling should be based on a well defined objective. For example, if the objective is to determine whether occupants were exposed to airborne mold spores, then air sampling would be recommended. Air sampling may also help to detect hidden mold growth.

Before sampling for mold, it is important to have a well defined objective.

Mold is a recognized health hazard. Every single day thousands of people who suspect they or their families are sick due to mold are looking for mold information from the Internet. But how reliable is the information posted on the Internet? Most of the mold information on the Internet is intended to create fear and panic so that the consumer of this information can buy a service or a product.

Where can one get reliable mold information?

Reliable information can be obtained from government sites, academic sites and a few private sites owned by mold experts. By mold experts, I mean people who studied molds at universities for their higher degrees. There are many self-proclaimed "mold experts" online.

Before believing what you read about mold online be sure you can trust the source of the information.

Many people get concerned if the black mold fungus called Stachybotrys appears in lab results even if only a few spores were reported. Some people conclude the results are okay if Stachybotrys was not present even when counts of other mold spores are relatively high. But is Stachybotrys the most dangerous indoor mold? Possibly not. Species of Aspergillus such as Aspergillus fumigatus, Aspergillus flavus and Aspergillus niger (A. niger is a black mold too) are well known health hazards. Personally I would not be concerned if a few spores of Stachybotrys are reported in air samples especially immediately after mold remediation.

Sampling Air For Bacteria
Bacteria air samples are taken by impacting air onto some suitable growth media. Two of the commonly used samplers are Andersen (N6 Single Stage) and Reuter Centrifugal sampler (RCS). The Andersen sampler uses petri-dishes while the RCS uses agar strips. For environmental bacteria, a general purpose media such as Tryptic (Trypticase) Soy Agar (TSA) can be used.


Sampling Surfaces For Bacteria
Sterile cotton swabs can be used to sample for bacteria contaminating surfaces. The swabs are then sent immediately to a laboratory for culturing and identification of the bacteria to genus or species.