Exposure limits for hazardous chemicals can be found in several locations.
There is the OSHA table of PELs, and the MSDS or SDS should also have this information.
Permissible Exposure Limits (PELs) are part of the OSHA regulations and are enforceable by law.
Usually (but not always) given as ppm, and usually (but not always) given as an 8h-TWA (8 hour time weighted average).
For example, the PEL for acetone is 1000 ppm 8h-TWA. An exposure of 2000 ppm for 4 hrs followed by 0 ppm for 4 hrs averages to 1000 ppm over the total 8 hrs, which is permissible.
Chloroform's PEL is not an 8hr-TWA, but a ceiling of 50 ppm. Employee exposures are never to exceed this concentration.
The OSHA table is located in the resources section available from the main menu.
Most of them are in table Z1,
with additional information in tables Z2
and Z3.
Table Z1 has the chemical name in the first column, the CAS number in the second column, and the PEL in ppm in the third column.
A C next to the PEL means that it is a ceiling value rather than a TWA.
