How to Test for Mold

Mold testing is an important step in the mold remediation process. It allows you to know what you are dealing with by saying conclusively if mold is present, identifying the types of molds in a given area, and even discover hidden mold growth. The two main types of mold testing are air sampling and surface sampling, but there are a variety of ways to accomplish both.

Air Sampling

An important aspect of testing for mold is air sampling. A variety of measurement meters, spore collectors, and air pumps can be used to gather air samples. It is important to sample the air outside of the building as well as inside of it. The results between the two should show similar mold counts. The ideal place to position an air collector for mold testing is three to six feet above the ground. You should take the outdoor sample at the same height as the indoor sample.

Before turning on an air pump, you need to calibrate the flow of the pump. You can do this with the use of a rotameter. The rotameter is a user-friendly air flow meter often used by mold inspectors. It consists of a tapered glass tube with a weight inside that is raised from the pressure of the pumped air and drops from gravity. The air flow rate can be determined by the position of the float at the time of testing.

The air-flow rate through an air pump must align with the manufacturer’s instructions. It is important to follow these instructions. If the flow rate is too slow, the spores will float around the collector plate without sticking and if the flow rate is too fast, then the spores will bounce off without sticking and not give you an adequate test for mold. Samples are recorded in spores per cubic meter (spores/m3). The pump should be calibrated daily to ensure a quality reading.

Next, attach the tubing to the pump and begin sampling the air. Make sure to monitor the air flow rate during the sampling process as it should remain consistent throughout. If the air flow changes by a percentage of five or more than you must stop sampling and start over again when you can get a consistent flow. Make sure to record the start and stop time of your sampling period as well.

When the sampling is complete, your collector slide should have a thin film of particles on it. If a slide is heavily covered, that may make results impossible to read and you should take a new sample. To calculate the volume of your sample, take the number of liters pumped and multiply that by the number of minutes in the sampling period. For example if you had 15 liters of air pumping for ten minutes then you will have an equation of 15 L x 10 min. = 150L. All air samples must have the same volume for consistent mold testing readings.

You must protect your used collector slides so they are not accidentally touched or contaminated, which would then alter the results. If there is an accident, simply use a new slide and take another sample.

mVOC Canister Sampling

Microbial volatile organic compounds (mVOCs) can be a sign that mold is actively growing in the area so testing for mVOCs is a common way to track down mold. Canisters can be used to quickly gather an air sample of the contaminated area. These are then sent to a lab to determine the concentration of mVOCs inside the space and whether there is cause for concern. Testing has shown that some people have allergic reactions at just 8 ug/L of total mVOCs.

Surface Sampling

Surface sampling helps to definitively determine if what you suspect might be mold on a surface is in fact microbial growth and it can measure how far along the growth is. There are a variety of ways to perform a surface sampling including swab, tape, carpet, and wall. When taking surface samplings for mold testing, you will want to take unique samples for each room, mold color, and mold surface that appears to be affected.

Swab Sampling

In a swab sampling, a moistened swab is contained in a tube, then removed and wiped across a one inch square area on a surface to garner a sample. You should see visible particles on the swab and then reinsert it into the tube. Different swab manufacturers may have different directions for their particular devices so be sure to read the instructions closely.

A swab test can immediately identify if a fungus is present and what type of fungus it is. This is a good test to utilize when mold is visible or if other signs of mold are present. It is a popular form of mold testing because it is cheap, quick,and can tell you every kind of mold that is present in the sample, even if the spores have not yet become airborne.

Tape Sampling

The tape method is the most common kind of surface sampling when testing for mold because you can take many samples quickly. Be sure to clearly label all of your tape samples since you will likely have many. This will also help you better organize your lab results.

To take a tape sample, you simply remove the slider as well as the protective liner (make sure the sticky side does not touch anything besides the surface sample area as this will contaminate results), put the sticky side down on the surface and press down gently to make sure it gets full contact, lift the slide and return it to its protective case. Then mail your samples to a laboratory and await your results.

Carpet Sampling

Taking a sample of a carpet involves the use of an air pump (set at 15 liters per minute), rotameter, carpet cartridge, and tubing. These tools are used to vacuum a small area of the carpet. Mold spores can remain deep inside of a carpet over a long period of time even after cleanings and vacuums, so they can provide insight into the history of the mold growth in that room. Refrain from deep cleaning the carpet before taking a sample as you want as much evidence as possible for your test. Choose a four inch by four inch area that gets little foot traffic, but not zero foot traffic like under the couch.

Insert the cartridge as deep as you can into the carpet and take your sample until you see particles collect on the cartridge filter. Do not exceed ten minutes of sampling time. If dirt appears on the filter, then throw this sample out and start again.

Wall Sampling

Sometimes a water damaged wall can be a small sign of what is hiding behind it. Therefore, mold testing may need to be performed in the cavity behind the wall. In order to do this, a small hole must be drilled into the wall (with written permission from the property owner beforehand). After the dust has settled from the drilling, insert the collection tube into the hole and turn on the air pump for about two minutes with a flow rate of 15 liters per minute.

Sometimes there are holes next to light switches and outlets where you can insert a collection tube to perform the wall sampling, which would allow you to avoid drilling into the wall altogether.

Proper Care of Testing Devices

It is important to clean all testing devices before and after use. If there is debris of any kind caught in the devices, it could drastically alter the results. After esting for mold, it is particularly important to thoroughly clean the instruments as there may be some mold spores remaining and improper cleaning may spread those spores to new areas.

Sampling devices and one-time-use tools should be stored in a cool, dry place. If slides, swabs, cassettes, or tapes are over a year old, then you should not use them and restock with fresh ones.