1926.55(a): Exposure Limits for Air Contaminants
Construction employers must limit workers' exposure to substances listed in Tables 1 and 2. Ceiling limits marked (C) must never be exceeded, assessed as a 15-minute average if instant monitoring is not feasible, and other limits must not be exceeded as an 8-hour time-weighted average in any work shift.
Key takeaways
- 1926.55(a) is part of OSHA's construction standards (29 CFR Part 1926, Subpart D).
- OSHA cited it 47 times in the last 3 years, in 47 inspections, with $523,340 in current penalties.
- 1 death is linked to inspections that cited this rule.
- Most citations: KY (7), WI (4), CT (4).
- Related part: 1926.55(a)(2) Other substances—8-hour Time Weighted Averages (34 citations).
- Free 5-minute toolbox talk for your crew below.
In this article
What this rule covers
29 CFR 1926.55(a) is one requirement inside 1926.55 Gases, vapors, fumes, dusts, and mists, an OSHA construction standard (Part 1926, Subpart D). It includes 2 sub-paragraphs. The official text below is copied word for word from the Electronic Code of Federal Regulations (eCFR). The numbers, injury cases and training on this page show how OSHA enforces it on real job sites.
Official text
(a) Employers must limit an employee's exposure to any substance listed in Table 1 or 2 of this section in accordance with the following: 47 citations
(1) Substances with limits preceded by (C)—Ceiling Values. An employee's exposure, as determined from breathing-zone air samples, to any substance in Table 1 of this section with a permissible exposure limit preceded by (C) must at no time exceed the exposure limit specified for that substance. If instantaneous monitoring is not feasible, then the employer must assess the ceiling as a 15-minute time-weighted average exposure that the employer cannot exceed at any time during the working day. 3 citations
(2) Other substances—8-hour Time Weighted Averages. An employee's exposure, as determined from breathing-zone air samples, to any substance in Table 1 or 2 of this section with a permissible exposure limit not preceded by (C) must not exceed the limit specified for that substance measured as an 8-hour time-weighted average in any work shift. Open (a)(2) 34 citations
Source: eCFR, text current as of 2026-10-15. Read all of 1926.55.
Injuries linked to this rule
1 death is linked to inspections where OSHA cited 1926.55(a).
At 5:28 p.m. on November 3, 2023, Employee #1 was employed by a specialty door contractor. Employee #1 had installed the first of four garage doors and was inthe process of completing the installation of the second garage door at a residential home. Employee #1…
Where and how often it was cited
| Year | Citations |
|---|---|
| 2023 | 3 |
| 2024 | 16 |
| 2025 | 9 |
| 2026 | 19 |
Top states: KY (7), WI (4), CT (4), ND (3), TN (3)
Largest penalties
| Employer | Location | Penalty for this rule |
|---|---|---|
| NORTHWEST CONTRACTING, INC. | BISMARCK, ND | $148,963 |
| RIEGER, BORGEN, BENSON ELECTRIC, INC. | BISMARCK, ND | $92,688 |
| NORTH TEXAS CONTRACTING, INC. | PLANO, TX | $16,550 |
| PKG CONTRACTING, INC. | SELBY, SD | $14,895 |
| WHITECO LLC | TOMAH, WI | $14,895 |
Free toolbox talk
A 5-minute crew talk on 1926.55(a), plus alerts when this rule changes. Free.
OSHA interpretation letters
- Whether it is mandatory to use a wet saw when cutting brick or concrete block. (2006-07-20)
- Allowable TLV of coke gases at the breathing levels of the employees. (1977-08-17)
Related parts of this rule
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Frequently asked questions
What is a ceiling value?
A limit marked (C) that the worker's exposure must at no time exceed.
How is a ceiling assessed if instant monitoring is not possible?
As a 15-minute time-weighted average exposure that cannot be exceeded at any time during the working day.
How are other limits measured?
As an 8-hour time-weighted average in any work shift, from breathing-zone air samples.
About this page
Sources
- 29 CFR 1926.55 (eCFR), text current as of 2026-10-15
- U.S. Department of Labor enforcement data: OSHA inspections, citations and accident records, copied nightly; data as of 2026-10-20
3-year window. Federal OSHA only; state-plan rules are not counted. Plain-language text is a summary, not legal advice; the official text controls. Black Belt Safety is not part of OSHA or the Department of Labor.