How Accurate are Air Mold Tests?
Are you concerned about the accuracy of your air test for mold? Don't know if the test will give accurate results for mold or not?
Don't worry in this ultimate guide you're going to find everything you wanted to know about the air mold tests and their accuracy.
To answer your question, the most precise way for assessing mold is by air sampling.
While a tape lift can precisely assess whether mold growth is present on a certain surface, it cannot tell you whether or not that mold growth has harmed the interior air quality by producing spores into the air. This can only be accomplished with an air sample.
Inhalation is the most common method of mold development exposure. As a result, monitoring the air for high amounts of mold spores is the most accurate technique to establish if the inhabitants are exposed to too much mold.
There are two kinds of air samples, non-viable and viable. Air is passed via an impactor device in both samples. The gadget draws in air and impacts it on a sticky material.
The airstrikes the surfaces and circulates the sides, while mold spores adhere to the surface.
Viable Mold testing
The spores on a Petri plate are impacted by viable samplers such as the Anderson Impactor. The mold development has a food supply in the petri dish. The mold develops over time, enabling the laboratory to determine the kind of mold.
Non-viable mold testing
A slit impaction sampler is generally used for non-viable testing. The Zefon Air-O-Cell cassette is a prominent example. These are little plastic cassettes with a tight entrance and a sticky inside surface.
Mold spores are dragged through the slit and contact the sticky surface. After collecting the samples, the lab opens the cassette and examines the slit surface with a microscope.
The laboratory can identify the genus and the number of spores, but not the species.
Check out our Non-Viable air test kit Here
Comparing Airborne Mold Testing Methods
The examination of viable or culturable materials takes a long period, usually 10-14 days. This is the length of time it takes for mold spores to start growing.
Non-viable samples may be processed as soon as possible, even on the same day if required.
A species-level analysis may be provided by viable samples. This is useful when seeking to establish a link between a specific health issue and an indoor mold problem.
While a non-viable sample might suggest a possible association, only a viable sample can verify the link.
When evaluating regions with highly immunocompromised people, viable samples are critical. Mold infections are a risk for these persons.
The small quantity of mold spores that can be quantified is a significant disadvantage of viable sampling. Only spores that can reproduce will be counted. All spores are counted in non-viable testing.
Non-viable spores may still cause allergies, therefore a viable sample may overlook a crucial mold exposure concern.
The cost is substantially greater due to the processing time necessary for a valid sample, which is sometimes 4-6 times as costly. In most cases, the non-viable sample is the ideal option due to its quick turnaround time and reduced cost.
There is also the concern of contamination with viable tests. In general, there are many more variables that can go wrong in viable testing. These variables lower the accuracy and can produce false positives or false negatives. Non-viable air sampling has a fraction of the variables to overcome in order to produce a “good” sample.
Air mold testing costs
A mold inspection/test normally has two components: a call-out charge and a per-sample price. If the sample is performed as part of a thorough inspection (which is almost usually preferable), the call-out charge is included in the inspection cost.
Most firms charge a basic examination price of $180-360 plus a per sample fee of $100-150. The key price variable is not the cost per unit, but the number of samples they propose.
This is where prices may swiftly spiral out of control.
On average, one sample per floor or 1,000 square feet is enough. Some firms would happily sell you the need of a dozen samples for your 800 square foot flat despite exceeding this recommendation.
This is the price for non-viable air samples. Specialty samples, such as cultured/viable samples, will be much more expensive.
As you will see later, sampling is not an exact science. It should be seen as a potential sign of a problem that needs to be investigated further, rather than conclusive proof of contamination.
Interpretation of mold testing laboratory data
Now that you have gathered the information, what should you do? This is when the problems begin.
Here's an example of a common mold testing scenario:
A homeowner employs a mold inspector to check their home. When they obtain the findings, they are informed that everything is great since the mold spore levels are well within the predicted range.
However, they are dubious about the outcome and employ another business to acquire a second opinion. Using the same methods, this inspector gathers additional mold samples.
The findings are sent to the homeowner within a few days. The spore counts are fairly comparable, but the second inspector advises them to leave immediately since their house has deadly amounts of mold.
Who is correct? What is up with the huge disparity?
The issue stems from a misunderstanding of how to interpret mold testing data. Unfortunately, no consensus exists on how to interpret this form of sample. The EPA does not have a policy on interpreting mold data. Other criteria exist, although their findings vary greatly.
Why is it so difficult to interpret mold testing data?
Mold testing difficulties are irritating but reasonable. Mold spores are everywhere. There are hundreds or thousands of mold spores floating in the air unless you are in a hermetically sealed clean environment.
However, this is not the major issue.
Mold testing can quickly determine the number of spores in a given volume of air.
The issue is a lack of consistency. Assume you gather one sample and then run another one an hour later. It would not be shocking if the number of spores increased by a factor of ten.
Is it possible that the room becomes plagued with mold all of a sudden? No. Perhaps there was a tiny change in the wind outdoors.
When the door was opened, maybe spores were drawn inside the room. Walking on a carpeted area may cause hundreds of spores to be released.
These are examples of variables affecting the outcome of samples.
As a result, mold testing can only analyze significant changes (or declines) from the baseline
A 10%, 15%, or even 20% rise or reduction above the control is statistically insignificant. We are searching for significant changes - usually of an order of magnitude. Technically, tiny adjustments may lead to significant results.
To do this, however, a significant number of samples must be collected. In most circumstances, this is both unworkable and prohibitively expensive.
There are three techniques in general: the Inside Comparison Method, the Outside Comparison Method, and the Fixed Standard Method.
Method of internal comparison
Mold testing using the inside comparison approach captures a sample in an unaffected area of the residence. This method is beneficial if the whole house is unclean and untidy.
In certain circumstances, mold spore levels in the whole home may be increased due to humidity issues unrelated to the region you are testing. This must be detected from the start, otherwise, the cleanup contractor may have difficulty passing a clearance test.
If this pre-sample is not obtained, the remediation effort may fail because mold spores from the rest of the house contaminate the containment zone.
The method of external comparison
This approach works on the same principles as the previous one, but instead of taking the comparison sample from a nearby region of the house, the sample is gathered from the outside.
This strategy is commonly utilized and effective in most situations. Keep in mind, however, that if it has just snowed, the outside control sample may be quite low. Again this is a variable affecting the data.
In these instances, even a tiny quantity of mold spores would be enough to trigger a failure. In these cases, a Fixed Standard approach would be preferable.
Instead of comparing mold spore counts in the confinement to the rest of the house, mold spore counts in the containment are compared to a pre-determined amount of acceptable mold spores.
Some standards, for example, use this strategy by establishing a threshold for certain forms of mold. i.e., the spore counts for Penicillium/Aspergillus, Stachybotrys, and Chaetomium cannot exceed a set number individually, and the overall number of spores cannot exceed 1,000 spores per M/3.
The limit for particular kinds of mold spores varies per spores per cubic meter. Others refer to the overall quantity of mold spores present, regardless of kind.
Combining different standards is often the best option. Mold spore levels are deemed increased, for example, if any of the following criteria are met:
The low threshold for Stachybotrys can be attributed to this spore being more dense (because it is usually only present when the water activity AW of a material is very high). Thus being more dense it is harder for it to become airborne. Many restoration firms will fail a sample if even 1 spore of Stachybotrys shows up.
Air Testing for Mold is an important tool that should be routinely used in mold inspections. But it is important to understand the limitations of this method. It should be used as a guide and a probe, but it is not intended to be the final verdict on air quality in a given home.
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