Use of TLs
The previous procedure can be used for assessing target levels for a variety of substances in work rooms with notable contaminant emissions. A different set of target levels has already been proposed for nonoccupied environments.14’15
In the design phase, “good industrial levels” should be set as the starting point, with design then proceeding according to the method described in Chapter 3. A target level should be set for dominant and critical contaminants in the space. For instance, for the welding of stainless steel, a target level should be set for hexavalent chromium, which is of concern as a health risk. If the “good industrial level” cannot be achieved—for example, due to the high emission of welding fumes—a higher target level can be considered.
Implementation of the target level procedure has clear benefits in both the short and long terms. The procedure is particularly useful in cases where the occupational exposure limit is later reduced. The reduction of exposure limits occurs from time to time in the light of new research information. For instance, for the occupational exposure limit of formaldehyde, the TLV given by ACGIH was reduced from 1.2 mg m~3 to 0.37 mg in-3 in 1992.15 The corresponding change took place in Finland in 1998. If the target level of formaldehyde was set just below 1.2 mg m~3, the performance of the whole ventilation system and other control systems would have been insufficient after the decrease of the TLV. Investments in a more efficient control technology are of benefit. If the original system was designed to comply with “good industrial level” (i. e. 0.1 mg m~3) or “general industrial level” (i. e., 0.2 mg m-3), no improvements would be needed regardless of the OEL reduction.
The setting of quantitative goals for indoor air quality also supports an organization’s quality policy in the area of safety and health. Furthermore, the introduction of the target level concept for indoor quality will enhance the development of more advanced and efficient control technologies on a voluntary basis. One can assume that the diffusion of technology will make the present-day benchmark air quality common practice in, say, 10 to 20 years.
Therefore, if the desired indoor air quality goals are clearly defined, they will benefit the designers, health and safety professionals, manufacturers of control technology equipment, end users, and other experts who are responsible for maintaining a safe and healthy indoor climate. In conclusion, introduction of the target level process for industrial air quality will benefit both the health sector and the production sector.
Posted in INDUSTRIAL VENTILATION DESIGN GUIDEBOOK