Dust sampling is a very useful tool of for IEQ investigation. Allergens and mold spores can be easily collected to help understanding the sources and reservoirs of those indoor bio-contaminants.

When collecting dust samples from carpet, bedding, and upholstered furniture, filter cassettes with 0.45 or 0.8 um pore sizes are good devices to use (Micro-vac). Cassettes with a collection tube may have higher collection efficiency than those that don't because of the way air flow go through the sample. Using 25 mm cassettes (with open face) can sample a larger area easier than using 25 or 37 mm cassettes with a collection tube. Higher flow rate may be needed for open-faced cassettes to collect dust.

Another way is to use common household vacuum cleaner or professional vacuum pump to collect dust samples using devices made of fabric or mesh (Macro- vac). The pore sizes can be as large as 30 um, which is way larger than most mold spores and allergens. Mold spores can easily pass through the devices. To efficiently collect sample, be sure to first collect dust from 10 to 20% of the area to be sampled. Visually inspect the devices to make sure enough of dust has coated the sampling area completely to create a much smaller passage than the original mesh has. After that, sample the rest of 80 to 90% of area with increased collection efficiency. If not enough dust from 10 to 20% of the collection area can be coated on the mesh, switch to Micro-Vac.

MCE, PC, and PVC are all good filter membrane materials. If MCE filter membrane is used, be sure to handle the sampling carefully. Do not press the cassettes onto the surface too hard and create a strong vacuum inside of cassette. When the cassette is removed from surface, a sudden release of that vacuum may break the membrane.

One dust sample cannot represent the bio- contaminants in the entire building regardless of how advanced the technology is (PCR or not). The pathway and history of bio-contaminant depository determine the outcome of settled dust composition, and it may not reflect the conditions in the whole building. A home seller can easily HEPA-vacuum or replace the carpet and magically transform a moldy house into a mold-free house if the consultants use ERMI as the sole investigation tool.

We have been helping companies that were frustrated with unsatisfying services from their microbiology labs on issues such as:
(1) poor technical support
(2) no personal attention
(3) questionable results
(4) project delay; slow turnaround time
(5) reports not making sense
(6) lack of ethics

Call us today, and understand how we can help you with that!

Host: Joe Hughes/Cliff Zlotnik

Episode Notes: After a long struggle that IAQ Radio followed closely for our listeners the revised and ANSI approved IICRC S-520 is finally available. We will discuss the major changes to the document, the process and why it took so long with our guest IICRC Standards Consultant, Mr. Larry Cooper. All this and more on the next episode of IAQ Radio.

Scheduled Time:
Date: Fri, October 3, 2008
Time: 12:00 PM EDT