The most important obligation for any employer is to ensure that workers are not harmed by exposure to toxic materials or conditions that may be present in the workplace environment. Exposure limits like the OSHA PEL, NIOSH REL and ACGIH® TLV® provide exposure limits, which if exceeded, may lead to immediate or long term harm. These guidelines and standards set the limits above which conditions are deemed to be hazardous. They are not necessarily the concentrations that should be used when setting alarms. For instrument users there are two obligations. The first is ensuring that workers are not exposed to hazardous conditions. The second is ensuring that workers are able to leave the affected area before becoming affected by a hazardous condition. Workers should be out of the area before rather than after the concentration of toxic gas exceeds the hazardous condition threshold. Unfortunately, the PEL, REL and TLV® are not always in agreement. Which exposure limit is applicable and enforceable depends on where you are, what you are doing, and who is responsible for enforcing your workplace safety requirements. Even when the applicable (and enforceable) hazardous condition threshold concentrations are unambiguous, setting the alarms can still be a challenge.
OSHA regulations use the term Permissible Exposure Limit (PEL) to define the maximum concentration of a listed contaminant to which an unprotected worker may be exposed during the course of his workplace duties. OSHA PELs are listed in Subpart Z (Section 1910.1000) of the Code of Federal Regulations, and in substance-specific standards (e.g., methylene chloride, 1910.1052 and benzene, 1910.1028) and posted at www.OSHA.gov. Individual states may either follow the Federal regulations, or if they have their own “Approved Occupational Safety and Health Plan” may follow their own, state-specific permissible exposure limits. States may not publish or follow exposure limits that are more permissive than Federal OSHA limits. Twenty-five states (as well as Puerto Rico and the Virgin Islands) have their own approved plan. The exposure limits in these jurisdictions are often more conservative than the Federal OSHA PELs.