Sampling Guide for Air Contaminants in the Workplace - Irsst

30 IRSST – Sampling Guide for Air Contaminants in the Workplace
It is important to minimize the time the petri dishes are open. Once sampling has been completed, the petri
dishes are hermetically sealed with a strip of parafilm and placed upside down to avoid the sample being
contaminated should condensation occur. All petri dishes must be identified with their place and time of
sampling. A self-adhesive label is placed on the side of the petri dishes. A blank must be produced for every
10 samples, or for each location if less than 10 samples are collected.
Warning
• The agar must never come in contact with anything.
• The inside of the head of the Andersen instrument must not be touched.
• Movements around the instruments must be kept to a minimum during sampling.
• Petri dishes must be kept closed for as long as possible.
• Sampling must begin immediately once the agar has been exposed to air.
• Sampling must be restarted if there is coughing or sneezing near the sampler.
• It is recommended that two samples be collected simultaneously.
Endotoxins are sampled on a glass fibre filter at 2 L/min for 4 hours.
2.5.3 Surface sampling
Occasionally, surface sampling by means of swabs, Bio-tape, sponges or samples of materials (bulk samples)
can be done on surfaces to locate sites of proliferation, but the interpretation of such results is complex and
can only be qualitative.
An initial approach suggests microscopic characterization of the mycological structures, which can help in the
rapid confirmation of the presence of a site of proliferation. This does not require growth; however, it does not
identify the strains present. It is important to note that characterization by mycological structure is not
achievable using swab samples.
A second approach proposes characterization following the growth of the viable microorganisms present in
the sample. This method is used to detect lower levels than mycological structure characterization because a
single viable cell can be detected if conditions favourable to its growth are met. This approach allows bacteria
and moulds to be analyzed. It is used for sponge or wipe samples and/or samples of various materials that can
provide information on the workers' probable exposure. It should be noted that identification by growth
cannot be done on Bio-tape.
Sterile swab sampling is done by rotating the swab on the surface to be sampled. A 100-cm² surface to be
sampled must be completely wiped with the swab to collect this sample. The entire surface of the agar is then
inoculated using the same principle of rotation. This method allows qualitative analysis only.
For microbial analyses on slides, sponges and bulk samples, refer to the sampling protocol (in French only)
available at the IRSST (23). Bio-tape is used for sampling smooth surfaces that are not contaminated by a
significant amount of material. The analyzed surface must not be made of friable material. After removing the
protective tape, apply the adhesive part of the slide to the surface to be sampled. Only the presence or absence
of mycological structures will be reported.
Sterile sponges are useful for sampling irregular dusty surfaces, or when large surfaces must be sampled. Use
the gloves provided and rub the sponge on the surface to be sampled. Place the sponge in the section of the
bag that was not previously opened. Sponge samples will be extracted and diluted before analysis. A too large
amount of material causes less interference with this type of analysis; however, a too small amount of moulds
will not be detected. It should be noted that contrary to the use of Bio-tape, sponge samples can subsequently
be used to identify microorganisms by growth.
Characterization by mycological structure and identification by growth of the microorganisms can be done on
a bulk sample when the material is suspected of being contaminated. Use alcohol for cleaning the tools that
will be used for sampling. It is preferable to use gloves (e.g., latex) for sampling. Place the sample in a clean
self-sealing bag or a sterile container (i.e., for a urine sample). The amount of material supplied must be
sufficient to allow appropriate analysis in the laboratory (minimum of one tablespoon or 10 mL).