Target Levels for Common Contaminants
The target level procedure was applied to 16 common air contaminants (Table 6.19). These are common contaminants in the industrial environment, and in many cases are the most critical compounds from the viewpoint of need for control measures. The prevailing concentration data as well as the benchmark levels were taken from Nordic databases, mainly the Finnish sources, and described elsewhere.12>1J! In addition, a general model for assessing target values for other contaminants is presented in the table.
The target levels for 16 common contaminants were grouped into four categories in terms of concentration bands. The numerical values of the target level categories II and III were obtained by using information on current concentrations in standard practice and benchmark plants. As an example, information on inorganic total dust is shown in (Fig. 6.9). The register of the occupational hygiene measurements revealed that the ratio of the current concentration levels to OELs depends greatly on the particular contaminant. Therefore, target levels are not given as the same fraction of the OEL. Excluding ozone and formaldehyde, the upper limit of “good industrial level” (category II) varies from 1% to 9% of the corresponding OEL in Finland. The upper limit of cat-
TABLE 6.19 A Classification Scheme of Target Levels for Common Air Contaminants in Industrial Settings
“As an example of special rooms, air quality requirements in electronics work rooms according to standard IEC 721-3-3 were used.
BA preliminary proposal, based on the fact that 5% of the current concentrations of formaldehyde are equal to or below this level.
‘The upper limit is the current OEL in Finland.
Egory “general industrial level" (category III) also varies from substance to substance. Again apart from ozone and formaldehyde, the limit is 10-34% of the corresponding OEL. Ozone is an exceptional
Compound because outdoor concentrations of ozone may be higher than indoor concentrations. Formaldehyde, which is one of the most common compounds in the manufactured environment, is also a critical contaminant, as the guideline value for residential air is relatively close to the corresponding OEL. It is worth emphasizing, however, that this scheme is still subject to further development.
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