# Methylene chloride — OSHA medical surveillance trigger thresholds by substance

For Methylene chloride, cfr section is 1910.1052; action level is 12.5 parts per million (ppm) calculated as an eight (8)-hour time-weighted average (TWA); pel is twenty-five parts of MC per million parts of air (25 ppm) as an 8-hour TWA; one hundred and twenty-five parts of MC per million parts of air (125 ppm) as determined over a sampling period of fifteen minutes; surveillance trigger is at or above the action level on 30 or more days per year, or above the 8-hour TWA PEL or the STEL on 10 or more days per year; exam frequency is Initial before assignment; for employees 45 years of age or older, within 12 months of initial or any subsequent surveillance; for employees younger than 45 years of age, within 36 months of initial or any subsequent surveillance; at termination or reassignment if six months or more have elapsed since last surveillance, recorded from its source on 2026-08-12.

- **Substance:** Methylene chloride _(verified: appears in the quote below)_
- **CFR section:** 1910.1052 _(verified: appears in the quote below)_
- **Action level:** 12.5 parts per million (ppm) calculated as an eight (8)-hour time-weighted average (TWA) _(verified: appears in the quote below)_
- **PEL:** twenty-five parts of MC per million parts of air (25 ppm) as an 8-hour TWA; one hundred and twenty-five parts of MC per million parts of air (125 ppm) as determined over a sampling period of fifteen minutes
- **Surveillance trigger:** at or above the action level on 30 or more days per year, or above the 8-hour TWA PEL or the STEL on 10 or more days per year
- **Exam frequency:** Initial before assignment; for employees 45 years of age or older, within 12 months of initial or any subsequent surveillance; for employees younger than 45 years of age, within 36 months of initial or any subsequent surveillance; at termination or reassignment if six months or more have elapsed since last surveillance
- **Record retention:** duration of employment plus thirty (30) years

## What the source says

> <https://www.law.cornell.edu/definitions/index.php?width=840&height=800&iframe=true&def_id=127ec2eccc47b064b95580991711b3ce&term_occur=999&term_src=Title:29:Subtitle:B:Chapter:XVII:Part:1910:1910.1052> Scope and application . This section applies to all occupational exposures to methylene chloride (MC), <https://www.law.cornell.edu/definitions/index.php?width=840&height=800&iframe=true&def_id=43beba05935babbe7c9b66c8d60a244e&term_occur=999&term_src=Title:29:Subtitle:B:Chapter:XVII:Part:1910:1910.1052> Chemical Abstracts <https://www.law.cornell.edu/definitions/index.php?width=840&height=800&iframe=true&def_id=7ab99fc89fa38fc3f0ffa4aeb1a0ae4b&term_occur=999&term_src=Title:29:Subtitle:B:Chapter:XVII:Part:1910:1910.1052> Service Registry Number 75-09-2, in general industry, construction and shipyard employment. (b) Definitions. For the purposes of this section , the following definitions shall apply: Action level means a concentration of airborne MC of 12.5 parts per million (ppm) calculated as an eight (8)-hour time-weighted average (TWA).

## Source

- https://www.law.cornell.edu/cfr/text/29/1910.1052

Last verified: 2026-08-12. Review by: 2027-02-08.
Part of [OSHA medical surveillance trigger thresholds by substance](https://referencesource.org/osha-medical-surveillance-triggers/).