Action level
An exposure below the legal limit that triggers requirements such as monitoring, medical surveillance or hearing conservation.
Definition, in the source's words
29 CFR 1910.95(c)(2)(opens ecfr.gov in a new tab)“For purposes of paragraphs (c) through (n) of this section, an 8-hour time-weighted average of 85 decibels or a dose of fifty percent shall also be referred to as the action level.”
Also defined in
29 CFR 1926.1153(b)(opens ecfr.gov in a new tab)“Action level means a concentration of airborne respirable crystalline silica of 25 µg/m 3, calculated as an 8-hour TWA.”
Also defined in
29 CFR 1926.62(b)(opens ecfr.gov in a new tab)“Action level means employee exposure, without regard to the use of respirators, to an airborne concentration of lead of 30 micrograms per cubic meter of air (30 µg/m 3) calculated as an 8-hour time-weighted average (TWA).”
What it means
Each standard sets its own action level. For noise it's 85 dBA (a 50% dose) against the 90 dBA PEL; for respirable crystalline silica 25 µg/m³ against a 50 µg/m³ PEL; for lead in construction 30 µg/m³ against 50 µg/m³.
Reaching the action level starts requirements even though the exposure is legal, such as a hearing conservation program under 1910.95(c)(1).
Example
A noise dosimeter shows a 50% dose for a press operator. The TWA is 16.61 × log10(50 ÷ 100) + 90 = 85 dBA, exactly the action level, so the operator goes into the hearing conservation program: audiograms, hearing protectors made available, and training.
Where it appears on the exam
ASP: ASP11 Domain 6, Industrial Hygiene and Occupational Health
CSP: CSP11 Domain 6, Occupational Health and Applied Science
Practice: Occupational Noise, Air Contaminants and Silica (General Industry)
CHST: CHST5 Domain 1, Hazard and Risk Identification and Control
Practice: Noise, Hearing Protection, Radiation and Lasers, Respirable Crystalline Silica in Construction, Lead in Construction
Questions
- What is the action level for noise?
- An 8-hour TWA of 85 dBA, or a dose of 50% (1910.95(c)(2)).
- Is the action level always half the PEL?
- No. Each standard sets its own number. Silica and lead in construction happen to be at or near half; learn each one.
Related
- Time-weighted average (TWA)
- Standard threshold shift (STS)
- Noise reduction rating (NRR)
- Formula: Noise TWA from dose
- Formula: Noise dose
- Regulation: 29 CFR 1910.95
- Regulation: 29 CFR 1926.62
Checked 2026-10-16. Spot a problem? Email hello@passcited.com.