Sampling Guide for Air Contaminants in the Workplace - Irsst

IRSST – Sampling Guide for Air Contaminants in the Workplace 5
1.1.2 Collecting information about the workplace
The second step involves collecting information about the processes and procedures in order to evaluate
the potential exposure to the identified contaminants. The purpose of this step is to generally describe the
following aspects:
• the tasks;
• the work organization;
• the process(es);
• the workplace layout;
• the safety methods and procedures;
• the emission sources;
• the ventilation and other means of control at source;
• the duration of exposure.
The health and safety records available in the establishment or at the government's OHS point of service
should be consulted to orient the intervention and to avoid unnecessary duplication.
1.1.3 Preliminary evaluation of the exposure
The third step , the preliminary evaluation of the exposure, tries to find a link between potential exposures
and the information about the workplace in order to attempt to establish the likelihood of an exposure. This
step takes into account the process parameters or the work methods that may result in the contaminant being
emitted into the worker's environment. For the process, these parameters are:
• the location and characteristics of each source;
• the number of emission sources;
• the emission rates for each source;
• the dispersion of the contaminant by air currents;
• the nature and effectiveness of the control measures (ventilation or elimination at source).
Most of the time, the parameters to consider in task execution are:
• The proximity of the worker to the emission sources;
• The time that the worker spends near the emission sources;
• The methods that may cause or increase the emissions.
Rapid qualitative evaluation methods can detect the presence or absence of a contaminant. Detector tubes,
even though they are not very selective or precise, provide interesting information about the presence and
relative concentrations of several contaminants. Direct-reading instruments are very useful tools at this step.
1.1.4 Studying available and relevant data
If the preliminary evaluation concludes that a contaminant is possibly present in the air, quantitative
information about potential exposures must be collected.
This quantitative information is obtained in the fourth step by studying the available and relevant data
originating from results collected previously in the worker's environment, in similar facilities and processes,
or calculated from satisfactory data, hypotheses or assumptions. If, in studying this data, it is impossible to
compare the exposure to reference values, a detailed evaluation of the exposure must be carried out.
1.1.5 Detailed evaluation of the exposure
A detailed evaluation of the exposure requires a statistically-supported rigorous approach to ensure that
the sampling is representative and that the results are correctly interpreted. However, with a concern for
efficiency and optimization of resource use, but without sacrificing scientific objectivity, the requirements