OSHA considers a time-weighted average of 100 parts per million (300 milligrams per cubic meter) over an eight-hour period as the permissible exposure limit.

The numbers are determined by taking a time-weighted average of values of a relevant operating parameter, such as temperature inside the reactor, in accordance with a smoothing algorithm.

This 8-hour time-weighted average is known as an exposure action value.

The key is to maintain an 8-hour time-weighted average of less than 85 dBA so that personal protective equipment is not required.

If engineering controls fail to maintain an 8-hour time-weighted average below 85 dBA, then a hearing protection device (hpd) is required.

The physical activity level is then the time-weighted average of the physical activity ratios.

Concentration of iodine in the air should not exceed 1 mg/m3 (eight-hour time-weighted average).

Exposure to them should not exceed 0.1 mg per m2 of skin in an 8-hour time-weighted average (40-hour work week).

It is usually (but not invariably) set somewhat above the relevant time-weighted average for the chemical.

The permissible exposure limit for osmium(VIII) oxide (8 hour time-weighted average) is 2 g/m.