Occupational Safety and Health Administration’s (OSHA) Hazardous Waste Operations and Emergency Response’s rule 29 CFR 1910.120 Section (h), titled “Monitoring” is a performance standard which entails initial and continued monitoring based on a hierarchy of standards for exposure to hazardous substances as well as situations for compliance protection of workers. This hierarchy for air contaminants consists of:

• OSHA permissible exposure limits (PELs),
• National Institute of Occupational Safety and Health (NIOSH) recommended exposure limits (PELs),
• American Conference of Governmental Industrial Hygienists threshold limit values (TLVs), and
• Other scientific information such as contained in Material Safety Data Sheets.

Dependent on site, hazards, and exposure specific considerations, therefore, an array of monitoring procedures may be employed to conform to the requirements of Section (h), to embrace decision-making about personal protection equipment.