Mold Testing: What You Need to Know

Mold Testing Colorado Springs only gives a snapshot estimate of the types and amount of mold present at a particular time and place. They may miss some types of molds and undercount others.

From a practical, health-protective perspective, visible mold growth indoors should be corrected regardless of the test results.mold

Many people become aware of a problem with mold in their home or business by visible signs, such as discolored spots on walls and floors, odors, respiratory symptoms, or watery or sticky surfaces. While these physical clues can indicate that a problem exists, identifying the types of mold present is a more complicated matter. Currently, most testing methods for mold only offer the ability to identify some live, viable molds. They may miss others that are not living or won’t grow on a culture medium used in the laboratory.

Most of the at-home mold test kits available to consumers use tape strips, swabs, or petri dishes for collecting a sample and sending it off to a lab for analysis. They are generally accurate in determining the genus of mold present, but they can be misleading if taken as a pass/fail test for a building or for making health-related decisions…

Another common testing method for mold involves drawing air through a filter and sending it to a lab for an analysis of the number of mold spores found in it. This is a useful way to find out whether spores are present in the air but is not effective in finding out where they are located or what types of mold they are.

Because indoor conditions of mechanical disturbance, ventilation, occupancy and usage vary widely over short intervals of minutes, quantitative results such as “spore counts” can be highly inaccurate and misleading unless a carefully designed time-weighted average is used. This is why we do not rely on air sampling as the sole method of determining a building’s characterization, nor would recommend to any inspector to do so.

In a few cases, we will collect an air sample from a dead air space such as behind a wall or above a ceiling in order to better understand a specific problem, but this is not often necessary. In most cases, the ERMI (Environmental Relative Moldiness Index) or HERTSMI-2 tests we use are more than sufficient for this purpose and provide a much more comprehensive result.

Surface Sampling

Surface sampling can be done as part of a mold inspection to help determine whether visible discoloration is fungal growth, to discover the types of fungi found on surfaces and in settled dust, and to track changes over time. This can be accomplished with a simple swab, a tape lift or a petri dish. A sample from the swab or petri dish is analyzed by a lab to see what organisms are present. This can also be used to identify mycotoxins (toxins produced by certain fungi) which can be toxic to humans and pets.

Surface samples are usually taken in areas of obvious mold growth, but can be used on other suspect materials as well. Typically, a sterile swab is rubbed across the surface to collect viable organisms which are then subcultured (grown) in a culture medium. The cultures are then viewed under a microscope to see what organisms are present. This type of analysis is also known as microbiological testing or microbial analysis.

Air samples are also analyzed in a variety of ways. The most common method is with a “spore trap sample.” A known volume of air is drawn through the spore trap sampling device and all particles that pass impact a sticky medium inside the device. Mold spores are a subset of these impacted particles and therefore adhere to, and are captured by, the sticky medium.

Other methods of analyzing air include swab samples, tape lifts and bulk sampling. Bulk samples are the best method, as they allow a representative sample to be collected without cutting up a wall, floor or carpet. Tape lifts require cutting up a small area, and swab samples can often be contaminated or destroyed during the collection process. These methods can also be expensive and take a long time to produce results.

It is important to remember that mold tests can only tell us what organisms are present, not how many or how much of each there is. It is also important to remember that health effects from molds are still poorly understood and that there is no level of mold exposure considered “safe” for occupants. Regardless, mold testing should be viewed as a supplement to a thorough visual inspection and should never be used as the sole basis for any remediation decision.

Mold Cultures

Molds are multinucleate fungi that derive their energy from organic compounds in the environment and through heterotrophic processes. They absorb nutrients through their hyphae and secrete hydrolytic enzymes that degrade complex biopolymers such as starch, cellulose and lignin into simpler substances the fungi can use. This enables them to play an important role in the decomposition of waste products and in the recycling of nutrients in ecosystems.

When an unknown organism is encountered in the field, a sample must be sent to a laboratory for identification. The material in which the organism is grown is called a medium, and the organism itself is known as a culture. The medium can be liquid or solid, depending on the sort of information one wishes to obtain.

Typical laboratory cultures are inoculated on a medium of nutrient-rich agar. The agar is poured into test tubes or bottles with narrow openings and sterilized. The cultures are then incubated and observed under a microscope. The growth pattern of the fungus is recorded and the organism identified.

A culture may be a smear of a suspicious substance, a piece of clear tape pressed against an area of interest, or a swab rubbed over the surface and then sent to the laboratory for examination. Once the samples arrive in the lab, they can be transferred to a microscope slide and stained with a colorant that the spores of the mold will absorb and deposit.

Most laboratories offer a wide variety of mold tests and identification services, from basic mycotoxin testing to ERMI and DNA-type mold identification. These tests are generally more expensive than air and surface sampling, but can provide valuable additional information that is not available from other tests. For example, a DNA test such as HERTSMI-2 can identify the presence of 36 different molds in a sample and provide information about which ones pose a health threat. However, the interpretation of the results is complicated and can often be done more efficiently by a qualified professional mold inspector. Often the simplest and most cost-effective approach is to have a professional conduct a thorough professional inspection and consultation.


There are many types of mold testing, ranging from simple do-it-yourself kits to sophisticated laboratory tests. All methods can detect spores in the air, on surfaces, and in settled dust, but they are not all equally reliable. Most tests only identify a portion of the live (viable) molds in the sampled environment and may miss or undercount those that are not alive or won’t grow well on the nutrients used to incubate the samples.

Even good testing can have errors, and people should always consult a professional to find the best solution for their individual situation. Testing should be done in conjunction with a professional mold inspection to determine the source of the mold and the extent of the problem.

Unless you have an allergy or sensitivity to specific types of mold, it’s usually safe and more cost effective to use at-home test kits that can identify common strains such as Stachybotrys and Penicillium/Aspergillus. These kits include one swab for each strain, two extra swabs if needed, a lab report request card and a pre-paid mailer. These kits run between $50 and $75 and can be useful for quickly identifying the presence of these common strains in a small area.

More expensive genus-level sampling by a laboratory can be conducted and is recommended when a person has a strong reaction to mold, or when there is a serious concern about a potential health impact. This testing identifies the genus of the mold and can help guide remediation efforts. Species-level testing is also possible and can be highly accurate, but is more costly and requires much longer turnaround times.

Molds can cause a variety of symptoms and effects, including respiratory irritation, allergic reactions, and damage to building materials and furnishings. Most of these symptoms are related to a buildup of mycotoxins, neurotoxins that are produced by some strains of mold and can be released into the air as a byproduct of fungi growth. It is important to note that mycotoxins are only found in the living cells of the fungi and are not present in dead or non-living portions of the organism. Because of this, it is very difficult for any mold test to reliably show the presence or absence of mycotoxins.

Tania Mendez