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Chemical Exposure TLV / PEL Lookup

Search occupational exposure limits, OSHA PEL, ACGIH TLV, NIOSH REL, and IDLH, for common workplace chemicals

Field guide: Understanding Chemical Exposure Limits: PEL, REL, and TLV

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Free chemical exposure limit database for industrial hygienists, safety professionals, and EHS managers. Search approximately 80 common workplace chemicals by name or CAS number to find the OSHA Permissible Exposure Limit (PEL), ACGIH Threshold Limit Value (TLV-TWA and TLV-STEL), NIOSH Recommended Exposure Limit (REL), and IDLH concentration. Includes exposure basis (8-hr TWA, 15-min STEL, ceiling), units (ppm, mg/m³), carcinogen designation (IARC, NTP, ACGIH A1/A2), and skin notation. Compare OSHA and ACGIH limits side by side, OSHA PELs are legally enforceable but often outdated, while ACGIH TLVs reflect current health science.

Pro Tip: Many OSHA PELs haven't been updated since 1971 and are based on 1968 ACGIH TLVs. For at least 100 chemicals, the current ACGIH TLV is 5 to 100 times lower than the OSHA PEL. While OSHA PELs are the legal floor, best practice is to use the most protective limit, which is usually the ACGIH TLV or NIOSH REL. Many employers adopt ACGIH TLVs as their internal action levels even though they're not legally required to.

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How It Works

  1. Search for a Chemical

    Type the chemical name, common trade name, or CAS number in the search field. The database matches partial names, typing "tol" will find toluene, typing "67-56" will find methanol by CAS number.

  2. Compare Exposure Limits

    View the OSHA PEL (legally enforceable), ACGIH TLV (health-based guideline), NIOSH REL (recommended limit), and IDLH (immediately dangerous to life or health). Note which limits are TWA (8-hour average), STEL (15-minute), or Ceiling (never exceed).

  3. Check Special Notations

    Look for the Skin notation (chemical absorbs through skin, air monitoring alone may not protect workers), carcinogen designations, and sensitizer flags. These affect monitoring strategy, PPE selection, and medical surveillance requirements.

Built For

  • Industrial hygienists planning air monitoring strategies and selecting sampling methods for workplace surveys
  • EHS managers comparing OSHA requirements to ACGIH recommendations when setting internal exposure action levels
  • Safety data sheet reviewers quickly verifying occupational exposure limits during chemical inventory reviews
  • Occupational health physicians evaluating worker exposure in the context of health surveillance programs
  • HAZWOPER supervisors identifying IDLH concentrations for emergency response planning and respiratory protection selection

Assumptions

  • Exposure limits are for healthy adult workers during an 8-hour workday, 40-hour workweek, they are not applicable to general population or environmental exposure.
  • Values shown are for the pure substance, mixtures may require additive exposure calculations per OSHA 29 CFR 1910.1000(d)(2)(i).
  • ACGIH TLVs are updated annually, the values shown are based on recently published data but should be confirmed against the current TLV booklet.

References

  1. OSHA 29 CFR 1910.1000, Tables Z-1, Z-2, and Z-3, Air Contaminants
  2. ACGIH, Threshold Limit Values and Biological Exposure Indices (current edition)
  3. NIOSH Pocket Guide to Chemical Hazards (NPG), DHHS (NIOSH) Publication 2005-149
  4. AIHA, WEEL (Workplace Environmental Exposure Levels) for chemicals without OSHA PELs or ACGIH TLVs

Frequently Asked Questions

PEL (Permissible Exposure Limit) is OSHA's legally enforceable workplace limit. TLV (Threshold Limit Value) is ACGIH's health-based guideline, not legally binding but updated annually with current science. REL (Recommended Exposure Limit) is NIOSH's recommendation, also not legally binding. IDLH (Immediately Dangerous to Life or Health) is the concentration above which a worker must use the highest level of respiratory protection (SCBA or airline with escape bottle). In practice, the TLV is usually the most protective for routine exposure.
Most OSHA PELs were adopted in 1971 from the 1968 ACGIH TLV list and have never been updated. OSHA attempted a comprehensive PEL update in 1989 (the Air Contaminants Standard), but it was vacated by the courts in 1993. Since then, OSHA has only updated a handful of individual PELs. Meanwhile, ACGIH reviews and updates TLVs annually based on new health effects research. The result is that many OSHA PELs no longer reflect current understanding of occupational health risks.
The Skin notation means the chemical can be absorbed through intact skin in amounts that contribute significantly to overall exposure. Air monitoring alone may underestimate total worker dose. Workers handling skin-notated chemicals need appropriate gloves, protective clothing, and potentially biological exposure monitoring (blood or urine testing) in addition to air sampling.
Both. The TWA (Time-Weighted Average) represents the average concentration over a full 8-hour shift, it protects against chronic health effects. The STEL (Short-Term Exposure Limit) is a 15-minute average that protects against acute irritation or toxicity from peak exposures. Some chemicals only have a Ceiling limit, meaning the concentration should never be exceeded even instantaneously. Your monitoring strategy should assess both average and peak exposures.
Disclaimer: This database is a reference tool and may not reflect the most recent updates to OSHA PELs, ACGIH TLVs, or NIOSH RELs. Always verify exposure limits against the current editions of OSHA 29 CFR 1910.1000 Table Z-1/Z-2/Z-3, the current ACGIH TLV booklet, and the NIOSH Pocket Guide to Chemical Hazards. Exposure limits do not represent sharp dividing lines between safe and dangerous concentrations.

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Understanding Chemical Exposure Limits: PEL, REL, and TLV

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