Alternaria mold spores and hyphae from an indoor surface (C) Daniel FriedmanVacuum Cassettes / Spore Traps for Mold, Particles, Dust

  • VACUUM CASSETTE FILTER SAMPLE TESTS for DUST / MOLD - CONTENTS: Field testing vacuum cassettes to collect building dust as a screen for toxic or allergenic mold contamination indoors. Guide to use of vacuum cassettes to screen building soft surfaces, furniture, carpeting. Guide to use of vacuum cassettes to collect multiple dust samples in buildings
  • POST a QUESTION or READ FAQs about using vacuum sampling methods to test for building dust or mold contamination
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Vacuum cassette test methods for building dust or mold:

This article explains the advantages and shortcomings of using vacuum cassettes or spore traps to collect mold test samples (or other dust or particle samples) from indoor surfaces such as carpets, couches, or multiple hard surface dust samples: How to do it & Guide to Good Dust Sampling Practices.

In this article series discuss the validity of nearly all of the popular mold testing methods currently in use, pointing out the strengths and weakness of each approach to mold sampling in the indoor environment, beginning with air sampling for airborne mold levels indoors.

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A Guide to Using Vacuum Samples for Screen Buildings for Toxic Mold

Portable hand vacuum (C) Daniel Friedman

[Click to enlarge any image]

15th Annual North Carolina/South Carolina
Environmental Information Association Technical Conference
Myrtle Beach, SC
Daniel Friedman 23 September 2005, Updated 4/14/2009 & 10/5/2012

A collection canister is connected to an air or vacuum pump which is used to draw particles onto a filter-surface or into a special collection container.

A collection device, slide, cassette, or tape are used with a calibrated air pump to collect surface particles.

The lab prepares a slide from the cassette (of the types below) or if an MCE filter cassette was used to collect particles, the lab clears the filter onto a microscope slide, washes the filter onto a microscope slide, or uses another method to transfer particles for examination by microscope for preparation by culture.

Our MOLD INFORMATION CENTER includes more broad discussions of the overall approach to building investigation, as do many expert references cited at that web. For a more comprehensive collection information about mold test methods see INDOOR AIR QUALITY METHODS COMPARED. For more on "mold classes" (Cosmetic mold vs. allergenic mold vs. toxic or pathogenic mold) see MOLD CLASSES, HAZARD LEVELS and more references such as a Mold Action Guide are at the end of this document.

Carpet vacuum test (C) Daniel Friedman

Using a simple portable pump calibrated to a known flow rate allows rough estimation of particle density per square inch of surface tested if that analysis is needed.

People using this approach may make use of a disposable paper square template that defines a precise surface area to be vacuumed (photo above left). In our opinion a precise quantitative approach to surface vacuuming is silly because there is normally large particle variation over building surfaces for many reasons. But the approach is useful to screen for high levels of particular particles (such as mold spores, animal dander, insect allergens).

Our photo (left) shows five vacuum test areas on a hallway carpet during a study conducted by the author to examine the variation in particle deposition by foot traffic in a residential hallway.

Our hypothesis was that more outside dirt and debris could always be found in the center of the main path of foot traffic even though that area also received more aggressive vacuum cleaning than the hallway sides. We have tested carpeting before and after various types of cleaning and after suffering various types of contamination.

Surface vacuuming for mold

Spore traps (C) Daniel Friedman

We emphasize that in this article we are discussing surface vacuuming to collect particles from an exposed surface onto which the vacuum device and collector can be placed directly.

This is an effective and useful particle or mold sampling method.

We are not referring building wall or ceiling cavity vacuuming methods that attempt to draw air and particles from the building cavity through a punctured opening and tube into a collecting device - an approach that our test found was ineffective.

We discuss building cavity vacuuming below at Vacuuming building cavities.

Couch test for mold or allergens (C) Daniel Friedman

Vacuum samples can be useful for testing soft goods (clothing, bedding, curtains, carpets) for high levels of contaminated spores in a qualitative approach. We particularly like vacuuming a number of surfaces in an area using a single collection device as a less-costly way to make a more confident inspection of the level of contamination by moldy dust in buildings with a known problem.

We also use this method as part of a mold clearance inspection to evaluate the thoroughness of both the containment system and the general cleaning effort. For example we may collect a sample of vacuumed surface dust from 10 different surfaces in 5 rooms on a floor of a home, forming a more broad screen for moldy dust than single tape lifts of surface dust.

We've found wide variety in levels of mold found growing in or on carpets, depending on a number of variables including even the level of other dirt present in the carpeting. Some experts question this measure. Carpet vacuuming for mold is interesting as a pre and post remediation baseline data source for areas out of the remediation/containment area, but for any carpet this method quickly overloads a particle sampler.

Burkard air sampler (C) Daniel Friedman

The Burkard personal air sampler (photo above) can also be used to vacuum particles from surfaces provided that a strong air flow is not required to lift the particles from the surface (this device pumps at 10 lpm).

Shortcomings of surface and carpet vacuuming for mold

  1. Vacuuming will not collect identifying structural components of mold as well as tape and will almost certainly damage or destroy the structures which it collects, imposing some limits on identification

  2. Vacuuming will not collect all of the material on a hard surface (which tape handles well). Particles which are easily lifted by the airflow into the canister will be over-represented compared with sticky particles which are adhered to the test surface.

    This problem is particularly sensitive to the flow rate (LPM) used. A low-flow rate (1LPM) avoids a sample overload problem (too many particles, can't read the sample) but may fail to collect or under-collect certain particles. A high flow rate improves particle pick-up but then limits the number of sample sites (increasing test cost) in order to avoid sample overload. We suspect that no vacuum method we have tested could reliably pull mold or debris reliably from deep inside a heavy upholstered couch.

  3. Carpet vacuums and some furniture or drapery vacuums will either be overloaded or restricted to culture (to which we have already objected).


Continue reading at VACUUMING BUILDING CAVITIES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



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