Monitoring in the workplace

12. Monitoring in the workplace
12.1. General principles
12.1.1. Employers should monitor and record the exposure of workers to
hazardous chemicals to ensure their safety and health. They should ensure that workers
are not exposed to chemicals to an extent which exceeds exposure limits or other
exposure criteria for the evaluation and control of the working environment. Based on
the monitoring data, employers should assess the exposure of workers to hazardous
12.1.2. Airborne concentrations of hazardous chemicals should be measured in all
places of work where this is necessary to ensure the safety and health of workers
against inhalation risks.
12.1.3. Measurements of airborne contaminants are necessary if other techniques
do not suffice to provide a valid estimate of the risk of exposure and to assess the
existing control measures.
12.1.4. Techniques for this risk assessment may include the following:
information on the intrinsic health and physical hazards, obtained from the chemical
safety data sheets; estimation of exposure based on the method of work and work
pattern; advice from the supplier; experience of exposure in the workplace or of other
users; and simple qualitative tests. Simple qualitative tests include, where appropriate,
the use of smoke tubes or pellets to determine ventilation characteristics, and of the
dust lamp for illuminating dust emissions.
12.1.5. The need for a programme for the measurement of airborne contaminants
should be based on the factors listed in paragraph 12.1.4, the extent of the exposure of
workers established as a result of the measurements taken, and the reliance on, and the
consequent need to check the effectiveness of, engineering control measures. Where the
need for a programme of measurements is determined for certain hazardous chemicals,
the monitoring strategy should be followed.
12.2. Measuring methods
12.2.1. Sampling equipment should be compatible with the analytical methods
available and should have been validated over a suitable range of concentrations above
and below the exposure limits or other exposure criteria in accordance with published
national or international standards, where they exist.
12.2.2. Static monitoring should be used to determine the distribution of an
airborne chemical throughout the general atmosphere of the working area and to
identify problems and priorities. Air samples should be taken:

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