What is OSHA permissible exposure limits?
Permissible exposure limits (PELs) are OSHA's legally enforceable limits on how much of an airborne substance a US worker may be exposed to, mostly set as 8-hour time-weighted averages.
Who must meet them
Employers under federal OSHA in general industry, with comparable tables for shipyards and construction. State plans can be stricter: Cal/OSHA sets carbon monoxide at 25 ppm, half the federal figure.
Key limits in Table Z-1
29 CFR 1910.1000 Table Z-1 lists limits as 8-hour averages unless marked as ceilings. Examples: carbon dioxide 5,000 ppm, carbon monoxide 50 ppm, ammonia 50 ppm, ozone 0.1 ppm, and particulates not otherwise regulated at 15 mg/m3 total dust and 5 mg/m3 respirable.
OSHA itself says most PELs were issued shortly after the OSH Act of 1970, have not been updated since, and many are outdated.
Where fixed sensors fit
PEL compliance rests on breathing-zone samples, which fixed sensors do not replace. Aqueduct adds a continuous zone record of CO2, carbon monoxide and VOC index across every shift, showing where and when levels climb, such as CO2 from trucks idling at a loading dock, so hygienists know where to sample.