Final answer:
The average airborne exposure not to be exceeded in an 8-hour shift or 40-hour work week is the Time-Weighted Average (TWA). Threshold Limit Value (TLV) and Short-Term Exposure Limit (STEL) are different exposure metrics, with TLV being the general exposure limit and STEL for short-duration exposure. The Ceiling Limit denotes the level not to be exceeded at any time.
Step-by-step explanation:
The average airborne exposure limit for any 8-hour work shift or 40-hour work week that cannot be exceeded is referred to as the Time-Weighted Average (TWA). This metric is used to assess the permissible concentration of a harmful substance in the workplace air over a standard workday and workweek. Threshold Limit Value (TLV) and Short-Term Exposure Limit (STEL) are other measurements, but TLV generally refers to airborne concentrations of substances and conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse health effects. STEL is a higher level of exposure allowed only for a short period of time, usually 15 to 30 minutes. The Ceiling Limit is the concentration that should not be exceeded at any time.
Exposure to particular levels of noise is a common example of why these limits are essential. For instance, levels like 85 dB should not be exceeded for 8-hour daily exposures without hearing protection, according to recommendations from various government agencies and health-related professional associations. This recommendation helps prevent hearing loss due to prolonged exposure to noise, such as those found in noisy factories or within heavy trucks. Extreme noise levels, like those from a jet airplane at 30 m, which can cause severe pain and damage in seconds, demonstrate the need for implementing strict exposure limits.