Permissible Exposure Limit. The PEL refers to the maximum air contaminant concentration a worker can be exposed on a repeated basis without developing adverse effects. The PELs are listed in 29 CFR 1910.1000 Tables Z-1, Z-2, Z-3. Also see: CFR 29 Section 1910 Subpart Z. For more information, see the Permissible Exposure Limitstopic page