1-866-4 JJSTECH(1-866-455-7832)

  1. Home
  2. Toxic Gases and Vapors Limits

Toxic Gases and Vapors Limits

Toxic Gases and Vapors

Toxic Gases and Vapors

Toxic atmospheres can come from:

  • Microbial action
  • Products or chemicals being used or stored
  • Work being performed
  • Areas adjacent to work area
Toxic atmospheres
Toxic atmospheres

USA Permissible Exposure Limit (PEL)

USA Permissible Exposure Limit
  • Determined by the United States Occupational Safety and Health Administration (OSHA)
  • Sets limits for legal unprotected worker exposure to a listed toxic substance
  • Force of law in USA!
  • Individual states free to enact stricter, but never less conservative limits
  • Given in "Parts-per-Million" (ppm) concentrations
    • 1 % = 10,000 ppm

Permissible Exposure Limits

  • "Parts-per-Million" (ppm) concentrations
    • 1.0 ppm the same as:
      • One automobile in bumper-to-bumper traffic from Cleveland to San Francisco
      • One inch in 16 miles
      • One minute in two years
      • One ounce in 32 tons
      • One cent in $10,000

Permissible Exposure Limits

  • "Parts-per-Billion" (ppb) concentrations
    • 1.0 ppb the same as:
      • One silver dollar in a roll of silver dollars stretching from Detroit to Salt Lake City
      • One kernel of corn in a 45-foot high, 16-foot diameter silo
      • One sheet in a roll of toilet paper stretching from New York to London
      • One second of time in 32 years

NIOSH Recommended Exposure Limit (REL)

NIOSH Recommended Exposure Limit
  • Determined by USA National Institute of Occupational Safety and Health (NIOSH)
  • Guidelines for control of potential health hazards
  • Usually more conservative than Federal OSHA exposure limits
  • Intended as recommendation but incorporated by adoption in many states with OSHA approved safety and health plans
  • Force of law in these states

Threshold Limit Value ( TLV ®)

  • Determined by American Conference of Governmental Industrial Hygienists (ACGIH)
  • Guidelines for control of potential health hazards
  • Intended as recommendation
  • Usually more conservative than Federal OSHA PEL, frequently more conservative than NIOSH REL
Threshold Limit Value

What are TLVs ®, and why do they matter?

  • In the United States which toxic exposure limits apply depends on:
    • The state in which the workplace is located
    • The type of work being performed (e..g. shipyard confined space entry versus general industry permit confined space entry)
    • Requirements that apply to a specific employer (e.g. US Coast Guard, Navy, Air Force, MSHA regulated worksites, etc.)
    • Corporate health and safety policies
  • The three most widely referenced toxic exposure limits for workers in the United States are:
    • United States Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs)
    • United States National Institute of Occupational Safety and Health (NIOSH) Recommended Exposure Limits (RELs)
    • American Conference of Governmental Industrial Hygienists (ACGIH ® ) Threshold Limit Values TLVs®

TLVs® Incorporated by Reference in:

  • NFPA 306