Warning

Settle Plate Application

Open the dish and set it on a surface such as a table and airborne spores will “settle out” on the plate. After exposing the plate, you will probably see colonies form after 24-48 hours. Can you then identify the type of mold? Probably not. It takes a considerable amount of knowledge and training to identify molds macroscopically, and even then, most microbiologists will hedge their bets until they can look at it under the microscope.This type of test implies it will indicate if mold spores are in your air.

What’s wrong with this test? Read More…

Mold spores will be found in every environment with the exception of “clean rooms” in some hospitals, manufacturing plants, and research facilities.

What do the authorities say about settle plate applications? Read the quote above by the ACGIH.

Some may try to quantify the results (i.e. 6 colonies grew); however, such results are practically meaningless. Why? First of all, not all spores in the air are viable (capable of growing a colony) or compatible with the media. Secondly, spores vary in size, shape and weight. Some settle faster than others. Third, did those spores originate from one of Mother Nature’s outdoor colonies or from an inappropriate indoor colony? If a gazillion colonies grow, it may indicate there is an indoor problem, however, if the outdoor air that day has 100 gazillion spores, maybe not.

What do Professional Mold Inspectors Use to test for mold?

Professionals typically use a special volumetric air impactor that draws a measured volume of air over the plate, and is designed to impact spores into the medium in a predictable manner. While drastically more accurate than settle plates, this type of test is still subject to the limitations of air testing and culturing.

Tip: From a practical point of view, the settle plate test simply confirms there are mold spores in the air (they really are there…normally). A similar test can be performed by setting out some used, moist coffee grounds on your counter and watch as the mold colonies form after a few days (or look in Uncle George’s not-so-clean refrigerator).

Air Conditioning Test Application

Tape or secure the petri dish to a supply vent on your air conditioning system. This type of test implies you will learn if mold is growing in your HVAC system. From a practical perspective, the growth of colonies resulting from this test means the HVAC system is moving air, just like its supposed to be doing.

What’s wrong with this test? Read More…

Same problem as above. Your HVAC system circulates air and spores are most likely in this air. Unless you have advanced filtering (i.e. HEPA-rated), you should expect to have mold spores being circulated as well. Even with advanced filtering, most HVAC systems suffer from filter by-pass problems, cabinet and duct leakage, etc. Like the settle plate test, if a gazillion colonies form, you may have an HVAC problem, but then again, maybe not. There are certain locations within an HVAC system where mold growth can be a problem. Remember, the main factors that are needed for mold growth are food and moisture so those are the areas to focus on. Mold won’t arbitrarily grow in your ductwork unless there is a significant problem.

Tip: Have the HVAC system inspected by someone who knows where the problem areas are located.

Visible Mold or Surface Test Application

Using a swab, transfer some mold from a visible colony to the petri dish, or swab a suspect surface for mold spores. Using growth media for source testing (visible mold) or surface testing for invisible spores are probably the best uses for these types of mold testing kits compared to air mold testing. However, they are typically not the most practical method for general fungal identification compared to tape-lifts and swabs.

What’s wrong with this test? Read More…

The probability of you experiencing false negative and false positive results is very high due to the inherent limitations of culturing biological specimens. Most professionals limit the use of culture testing to applications where identifying the organism to a species-level is desired. In this case, the genus (type) of mold is known or suspected, and the proper media is selected based on providing optimum growth for that particular organism. Since optimum growth is dependent on a number of factors including temperature and time, specimens are often packed in temperature-controlled containers and expedited to the lab for incubation.