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PHOTO of sewage contamination sludge on the floor in a basement from a sewer line backupSterile Swab Test Kits
How & when to use a swab test kit

Sterile swab test kits:

Here we explain the steps in using a sterile swab to test a building surface for evidence of sewage contamination or for other purposes such as collecting surface contents to screen for pesticide application, mold (questionable) or other indoor contaminants.

Page top photo: sewage debris remnants on a concrete floor after a sewage backup in a New York home. Testing to confirm this condition is not necessary, but swab testing might be used after the sewage cleanup-job to confirm that the cleaning and sanitation steps were adequate.

This article series explains how to deal with and test for various types of environmental contamination in and around buildings.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Sterile Swab Test Procedures

Swab sample surface selection guide (C) Daniel FriedmanTypical sampling methods to test for sewage contamination in buildings and some other forensic or environmental tests such as the collection of material to test for pesticide or mold, include use of sterile swabs on sample surfaces both in the suspected area and as a control in other building areas where low or no contamination is expected.

In our photo is a cardboard rectangle used to guide the size of sample area for surface particle tests. Such a paper rectangle can be suitable for use in marking off an area to be tested using a sterile swab.

Sampling templates are sold in two sizes: 4 x 5cm (20cm2) and 10 x 10cm (100cm2). For sterile swab sampling you will probably want to use the 100 cm2 size.

Step by step details of how sterile swabs are used to collect environmental samples of suspected mold, sewage, pesticide residue, or other substances are found here.

  1. Choose the test surface: A rectangular area of about 10 x 10 cm (4 sq. in.) is marked or selected in a representative area of surface to be tested for sewage contamination.

    Some sterile swab tests kits include a heavy paper square with a rectangular 10 x10 cm cutout in its center to permit very precise area measurements for this test .
  2. Wearing appropriate protective clothing for working in a sewage contamination area (booties, coveralls, respirator, eye protection, sterile gloves) or in other hazardous areas such as a badly-contaminated moldy building.
  3. Choose the sterile swab test kit: a sterile swab is used to swab the test area.

Below: Copan sterile swabs used by the author for surface sampling for bacterial contamination such as proof of adequate clean-up after a sewage contamination problem in a building.

Copan sterile swabs suitable for sewage contamination test (C) Daniel Friedman

  1. Wipe the swab on the test surface: The swab is wiped sequentially across the test area using light pressure in a series of straight lines to cover the test area. I rotate the swab during this procedure so that all of its surface has been in contact with the test area as I move through it.
  2. Save the swab: The dampened swab is inserted back into the sterile tube, obviously with the swab-end going first, down into the tube.
  3. Label the swab sample: The swab container is then sealed and labelled.
  4. Use a chain of custody document: Log the sample in to your chain of custody sheet. Include the property address, date, time, location of the sample, size of the area swabbed, and your contact information.

    The information chain of custody serves more than to provide legal documentation of your test sample. It also provides information needed by the environmental test laboratory who will process your sample.
  5. Mail the sewage contamination test swab kit to a test laboratory equipped to process the swab to identify the bacterial pathogens it has collected. Be sure to indicate to the test laboratory the tests that you want wanted.

    Many water test labs can provide this service. For sewage contamination tests that might include

    E. Coli and/or Enterococcus, Fecal Coliforms, and Total Coliforms.

    Enterococcus is a good sewage contamination indicator since it indicates fecal waste from humans or other animals. However Enterococcus can also derive from some plants.

    It is important that you do not simply have a lab test for total coliforms since that can include non-sewage or non-septic bacteria. E. Coli is specific to sewage, but the level of bacteria found in the sample is important in its interpretation, since some E. Coli could be tracked onto a building floor simply from soil particles.

    The fact that bacteria of all of these indicator types can be present without an actual sewage spill in a building explains why you need to discuss the test with your test lab and why with some lab results you may need to ask the lab manager to help interpret the result.

We also use UV light to screen buildings for sewage contaminants, urine, or other body fluids, including blood. See

Where to Buy a Sterile Swab Test Kit & Chain of Custody Forms

Copan sterile swab example, used for sewage contamination test at InspectApedia.comSterile swab test kits are widely sold by online suppliers of environmental tests and other specialty suppliers. Below we'll list some swab test kit manufacturers or large suppliers.

The sterile swab is normally a synthetic fibre such as rayon, not cotton. Sterile swab test kits are provided in a sterile container in which a sponge has been pre-moistened with a sterile solution.

For bacterial swab tests such as a test for sewage contaminants the wetting agent might be 1.5ml of phosphate-buffered saline (PBS) at the required pH of 7.2. That solution preserves and stabilizes the sample.

Watch out: using a swab test kit to screen for mold has significant deficiencies and is not a procedure we recommend. Swabbing destroys physical particles that might be used for direct microscopic identification of mold, and use of a swab to culture mold, while suitable for some medical procedures, is not reliable as a building contamination screen.

See MOLD CULTURE TEST KIT VALIDITY for details.

Copan sterile swab information (C) Daniel Friedman InspectApedia.com

InspectAPedia.com is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website. We do not sell products nor services.


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