BS 482:2006 pdf download – Workplace atmospheres — General requirements for the performance of procedures for the measurement of chemical agents
In this document measuring procedures are classified according to measurement task. This classification isbased upon the measurement strategy laid down in EN 689.
NOTE EN 689 describes a number of measurement categories that involve a combination of these measurementtasks (see Annex A).
4.2Screening measurements of time weighted average concentration
Screening measurements of time weighted average concentration are performed to obtain relatively crudequantitative information on exposure levels in order to decide if an exposure problem exists,and if so, toappraise its possible seriousness.These measurements can also determine if the exposure is well below orwell above the (occupational exposure) limit value.
4.3Screening measurements of variation of concentration in time and/or spaceScreening measurements of variation of concentration in time and/or space are used to:
– provide information on the likely pattern of the concentration of chemical agents in air;
-identify locations and periods of elevated exposure;
– provide information on the location and intensity of emission sources;
-estimate the effectiveness of ventilation or other technical measures.
4.4Measurements for comparison with (occupational exposure) limit values and periodic
Measurements for comparison with (occupational exposure) limit values are used to obtain results of knownprecision and accuracy for the average concentration of a chemical agent in the air in a worker’s breathingzone.
Periodic measurements are used to determine whether exposure conditions have changed since themeasurements for comparison wit limit values were performed, or whether control measures remain effective(see EN 689).
NOTE Since the composition of the workplace atmosphere will have been investigated during the initial occupationalexposure assessment, it might be appropriate for periodic measurements to use procedures with lower selectivity.
NOTE Performance requirements for measuring procedures depend on the measurement task. The performancerequirements for screening measurements are less stringent than for measurements for the comparison with limit valuesand periodic measurements. Therefore, the performance requirements for screening measurements in 5.1 and 5.2 areonly given in general terms.
5.1 Screening measurements of time weighted average concentrationThe measurement procedures shall have:
adequate selectivity for the chemical agent (see 4.2);
averaging time less than or equal to the limit value reference period;measuring range that includes the limit value;
expanded uncertainty that is fit for purpose (see 4.2).
5.2Screening measurements of variation of concentration in time and/or spaceThe measuring procedures shall have:
adequate selectivity for the chemical agent (see 4.3);
short averaging time (for variation of concentration in time 5 min; for variation of concentration inspace ≤ 15 min);
measuring range that is fit for purpose (see 4.3);
-expanded uncertainty that is fit for purpose (see 4.3).
5.3 Measurements for comparison with limit values and periodic measurements5.
A measuring procedure shall produce an unambiguous result for the concentration of the chemical agentbeing measured in the specified measuring range, i.e. an analytically determined value shall correspond toone concentration only.
The measuring procedure shall contain appropriate information about the nature and magnitude of anyinterferences.
NOTE Selectivity requirements vary from case to case, depending on what is known in advance about the workplaceair. If the identity of all contaminants present is not known in advance then the measuring procedure will need to have ahigh selectivity. if the identity of all contaminants is known prior to measurement, and there are no interferents present,then it might be possible to use a measurement method with a low selectivity.
5.3.3 Averaging time
The averaging time is equal to the sampling time, which shall be less than or equal to limit value reference period.
5.3.4 Measuring range
The measuring range of the procedure or instrument shall cover at least the concentrations from 0,1 to 2 times the limit value for long-term measurements and from 0,5 to 2 times the limit value for short-term
5.3.5 Expanded uncertainty
The requirements for expanded uncertainty are given in Table 1.