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• 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?

Here we explainwhat Mold Concentration Bursts are and we explain 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. Readers should also see Mold Spore Counts: are indoor fungal spore counts valid?, and for a more in-depth critique of popular mold testing methods than this tutorial see Mold Sampling Methods in the Indoor Environment © Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

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 my 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.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

ACCURACY OF VARIOUS MOLD TEST METHODS
  Causes of Variation in Airborne Particle Levels
  Indoor vs. Outdoor Spore Counts
  Extent of Variation of Airborne Particle Counts
  Particle Levels vs Sampler Height
  Particle Levels vs Windows/Doors
  Particle Levels in Ducts
  Concentration Bursts of Mold Spores
  False Negative Results in Mold Tests
  Mold Culture Plate Test Errors
  Why Use Airborne Mold/Particle Sampling?
  Visual Inspection and History for Mold

Technical Reviewers & References

Particular thanks are due to experts and also consumers who read these articles and suggest corrections, changes, and additions to the material.

• Thanks to Susan Flappan, Flappan Consulting, moldetect.com, Overland Park KS, 913-402-1131, for contributing comments and some suggested text from ACGIH Bioaerosols: Assessment and Remediation 12/2006.
• Daniel Friedman - principal author/editor of the InspectAPedia ^TM Website
• Technical reviewers are invited to comment or ask questions - contact us

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