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Action level: what it means for the CHST

Toe Board editorial teamSources checked 3 min read

An action level is an exposure value, set below the permissible exposure limit, that switches on certain employer duties such as repeat air monitoring, medical surveillance and training. It is an early warning: a worker at the action level is still under the legal limit, but close enough that the employer must start watching.

A vertical exposure scale with two marks: a lower dashed line labeled action level, which starts monitoring and medical checks, and a higher solid line labeled PEL, the legal limit
The action level is the trigger for watching. The PEL is the limit.

The numbers to know

Our health hazards guide sets out the two that come up most in construction:

  • Respirable crystalline silica, 1926.1153: action level 25 micrograms per cubic meter, PEL 50, both as 8-hour averages.
  • Lead, 1926.62: action level 30 micrograms per cubic meter, PEL 50.

Silica and lead share a PEL of 50 but have different action levels, which makes them easy to mix up.

What the action level triggers

The exact duties differ by standard, so read the one that applies. In general:

  • Monitoring. Exposure at or above the action level means sampling is repeated on a schedule. Results below it, confirmed, can let the employer stop sampling.
  • Medical surveillance. Under the lead rule, workers exposed to lead at the action level on more than 30 days in a year get medical surveillance including blood lead testing.
  • Training and information. Under the lead rule, workers exposed at or above the action level get specific training on the hazard.

Under the silica rule, an employer who follows the silica Table 1 controls fully for a task does not have to assess exposure for that task, so the action level matters most to employers who measure instead.

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Noise is the odd one out

The 85 dBA action level that many people learn belongs to the general industry noise rule, 1910.95, which ties a hearing conservation program to it. The construction rule, 1926.52, sets its table of permissible levels from 90 dBA for 8 hours and asks for a continuing hearing conservation program where exposure is above the table. Cite the right part.

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Common mix-ups

  • The action level is not a second PEL. Being over it is not a violation; failing to do the duties it triggers can be.
  • Half the PEL is not a rule. Silica's action level happens to be half its PEL. Lead's is not.
  • Respirators are tied to the PEL, not the action level, under the lead standard (1926.62). The action level drives watching, not breathing protection.

On the CHST exam

Silica, lead and noise are named in the hazard and risk identification and control domain, 36.6% of the CHST. Learn each action level together with its permissible exposure limit.

Practice it

The CHST terms glossary lists every term in this set, including the time-weighted average both numbers are measured as.

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Sources

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Facts checked 26 October 2026 against the sources listed above. If something has changed, tell us and we will correct it within 2 business days.

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