May 10th, 2017 11:28 AM by Dan Howard
We often get asked about the Petri Dish mold test kits you find in hardware stores, grocery stores and the like. You’ve seen these hanging on racks at the end of aisles. They are the colorful packages showing gross mold pictures calling your name to come purchase. Just to add insult to injury, the plastic packs they come in will require a machete and crowbar to open.
They are inexpensive. Actually, let’s call it as it is, as compared to a professional mold assessment they are downright cheap.
The problem is that they provide as little useful information as they cost.
There are a bunch of reasons for their being next to useless (except to the people selling them as this is a multimillion dollar business).
Only about 10% of all molds will grow on any culture medium many molds will only grow on specific cultures. There are literally hundreds of culture media mycologists have developed to try to coax mold to grow in the laboratory. When we order cultures, we are offered have pages of choices for use in hundreds of situations. What this means is that you are potentially missing 90% of the molds that could be growing in the area being tested. You’ve heard the old saying, “you don’t know what you don’t know” and that may be essential information to correct the mold issue in your property.
The rate and area that mold spores fall is irregular and not representative of the area being tested. When a Petri dish culture is set out, the character of the air currents and ability of different size and shape spores to travel is not predicable or certain. Think of it like the spore population gets on an airplane, but you do not know where they are going to land and can’t predict what gate in which city they are going to land. In that case, you can’t place the Petri dish where it needs to be to meet the spore traps “at the gate”
The Petri Dish sample does not tell you how much of a mold is in the area. Last year I sowed zinnias in 3 separate pots, side by side. They were sitting on the patio with the same amount of light, water and temperature. The Zinnias grew at different rates in each pot. The variable was the soil in each. One had fresh soil and the others I had not changed the soil in the pots from the previous year. The amount of time that the Petri dish spends in the store and your home before use, and the temperature can affect the growth rate. The suitability of the agar for each mold growing in the Petri dish will also affect growth rate.
Simply put: How much and what type of mold is critical to understand if there is a problem in a building that requires remediation and to determine the type of appropriate remediation scope and products. The mold professional also needs to understand the materials and methods of construction and location of the underlying causes of the mold contamination to make sure that the mold does not come back.
Save yourself the $10.00 for the test kit and $30.00-$40.00 and up lab fee.
A site assessment and air testing are critical to resolving mold issues so that they do not return. The “Do-It-Yourself” kit does not reliably offer you any of that information. We want your home to be healthy and stay that way.