Lady analyzing air sampling samples under the microscope. ABOUT AIR SAMPLING PROBLEMS

Some clients assume that a mold laboratory’s results are the most important part of a mold investigation. They feel that mold test results will always be accurate. Unfortunately, this is not always true. Lab results are an important part of any mold inspection. We always take samples. However, it is important to note that their are many air sampling problems. As a result samples are not to be blindly relied upon.

Sample results have many limitations, and therefore should never be considered as a complete picture.

One reason for this is several little known about air sampling problems. For example air samples are variable and not always accurate, this must be taken into consideration when looking at lab results. Some reasons why mold sample results may not always be accurate are below.

 

TRAPPED SPORES

If mold growth is concealed under paint, inside a wall, or behind a baseboard, or cabinet, the mold can cause health complaints. Trapped spores may not escape and as a result may not show up in an air sample. Microbial volatile organic compounds can escape and cause health complaints and odors even when spores remain trapped. Because mold is often hidden this becomes a very important consideration. In such cases an inspector will have to do an inspection for subtle clues. Inspectors must use judgment and observations to determine if mold may be hidden. Room air sampling alone is often useless and gives false negatives when mold is hidden.

 

MOLD TEST RESULT VARIBILITY

Another problem with air sampling for mold is test result variability. You can sample the air from a room, and minutes later sample again and come up with completely different test results. Of you can take a sample from one location and find different results just a few feet away.

ait testing kit

Air Testing Kit

 

EXAMPLE 1


Imagine you are in a home with mold behind an oven, sink, or cabinets. In addition, no AC or ceiling fans are disturbing the mold on the walls. The mold type is Stachybotrys, and it is wet from a recent kitchen sink leak. This mold produces spores that are not easily released into the air when wet. You have to disturb them with drops of water splashing on them, or with air blowing across them for them to become airborne. An air sample is taken from the kitchen island 6 foot away from the blocked moldy walls. In such a case the air samples may not pick up any Stachybotrys mold problems despite a serious problem 6 foot away.

Now take that sample next to the oven with the pump exhaust pointing towards the area behind the oven. The exhaust air blows behind the oven and stirs up spores behind the oven and you come up with many Stachybotrys spores in the sample.

 

EXAMPL 2

Now imagine you are at a different property. A sample is taken, you do not know it but a two-inch area of carpet is slightly moldy.  No big deal, a spilled cup of water wet the floor last month. Twenty minutes before the sample was taken that carpet was vacuumed. Vacuuming stirred up thousands of spores from a small two-inch colony in the carpet. Only a small area of carpet was lightly contaminated but that tiny growth made the entire rooms air seem moldy in the lab results.

ENVIRONMENTAL FACTORS EFFECTING SAMPLING 

Here are some examples of environmental factors that can cause mold sample errors or limitations. These factors all cause great varibility in sample results.

  • The AC blower fan turning on.
  • Same blower fan turning off.
  • A ceiling fan is in use.
  • The same ceiling fan is not in use.
  • The presence of settled spores on a floor where foot traffic is occurring.
  • Actual mold colonies growing on a floor where foot traffic is occurring.
  • The amount, frequency, and duration, of foot traffic.
  • Sweeping, dusting, or vacuuming causing spores to become airborne just prior to sampling.
  • Proximity of a sampling pump to mold growth.
  • Sampling pump orientation, (pump exhaust air blowing and stirring up spores V.S. blowing away from mold.)
  • Wind blowing air into an open window from a landfill or from an agricultural area with freshly tilled soil may be moldy.
  • Wind blowing air into an open window from a wet lumberyard may be moldy.
  • Ocean breezes entering a property may carry very few spores and may dilute otherwise moldy indoor air during testing.

Inspector doing his job.

THE INSPECTORS PART

As you can see many common factors can cause differenced in sample results. This is why your local areas mold inspector must not rely on test results alone. An inspector must know how to conduct a proper mold inspection. They must interview the clients about the buildings water and mold related history. An inspector must use his or her own personal observations, and common sense when doing an investigation.

IN CONCLUSION

In conclusion, sampling for mold can give false results. Mold samples are not perfect, they are just one of many tools and should not be relied on to answer all the questions related to how moldy a building is. For more info on this topic see part 2 of this article here.