Photograph of Allergenco Mark III Impaction Air Sampler Mold Mold Concentration Burst Error in Mold Tests

  • CONCENTRATION BURSTS of MOLD SPORES - CONTENTS: What are Mold Concentration Bursts and how do they cause Errors in Mold Tests when using Air Sampling?
  • What are the sources of variation in the mold level that air tests can detect?

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Mold concentration bursts impact on airborne mold count results: here we explain what Mold Concentration Bursts are and how mold concentration bursts cause Error in Mold Tests when Air Sampling. This document is a brief tutorial which provides information about the accuracy of and sources of errors in tests for the level of allergenic and toxic mold in residential buildings: Are spore counts valid? Are cultures and swab tests valid? These critical questions are discussed in this paper.

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Concentration Bursts of Mold Spores Cause Variation in Indoor or Outdoor Mold Level Counts

ACGIH Bioaerosols: Assessment and Remediation states [section 1.2.3]:
Some organisms and sources release aerosols as 'concentration bursts' which may only rarely be detected by limited grab sampling and may be masked in measurements of long-term average concentrations. Nevertheless, such episodic bioaerosol releases may produce significant health effects. -- thanks to S. Flappan for suggesting this citation.

Spores are not always airborne during sampling: Mold spores may not be in interior air at the time of the sample but may be present in high levels at other times. Particle level in air varies very continuously as a function of temperature, humidity, size, mechanical disturbance, HVAC operation, use of fans and vacuum cleaners, and other factors as simple as foot traffic through a building.

Concentration bursts of mold spores: An example of a concentration burst of Aspergillus sp. spores occurred during our inspection and monitoring of a college library with many moldy books in its basement. Initially, though there was a large area of visible green mold (Aspergillus sp.) on many books on shelves in the library basement, while conditions there were still quite damp (humidity 65-75% RH) the airborne Aspergillus sp. spore levels were rather low.

But when the college brought in an "expert" who installed commercial dehumidifiers (without cleaning or removing the mold) the airborne Aspergillus sp. skyrocketed. As the humidity dropped the fungus responded by releasing spores.

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