1926.651(g): Hazardous Atmospheres in Excavations
Employers must test the air in excavations greater than 4 feet deep before employees enter where oxygen deficiency (less than 19.5 percent oxygen) or a hazardous atmosphere exists or could reasonably be expected. They must protect workers with ventilation or respirators, keep flammable gas from exceeding 20 percent of the lower flammable limit, retest when controls are used, and keep attended rescue equipment readily available.
Key takeaways
- 1926.651(g) is part of OSHA's construction standards (29 CFR Part 1926, Subpart P).
- OSHA cited it 19 times in the last 3 years, in 17 inspections, with $54,289 in current penalties.
- Most citations: PA (3), NC (3), AR (2).
- Related part: 1926.651(g)(1) Testing and controls (16 citations).
- Free 5-minute toolbox talk for your crew below.
In this article
What this rule covers
29 CFR 1926.651(g) ("Hazardous atmospheres") is one requirement inside 1926.651 Specific excavation requirements, an OSHA construction standard (Part 1926, Subpart P). It includes 8 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
(g) Hazardous atmospheres — 19 citations
(1) Testing and controls. In addition to the requirements set forth in subparts D and E of this part (29 CFR 1926.50-1926.107) to prevent exposure to harmful levels of atmospheric contaminants and to assure acceptable atmospheric conditions, the following requirements shall apply: Open (g)(1) 16 citations
(i) Where oxygen deficiency (atmospheres containing less than 19.5 percent oxygen) or a hazardous atmosphere exists or could reasonably be expected to exist, such as in excavations in landfill areas or excavations in areas where hazardous substances are stored nearby, the atmospheres in the excavation shall be tested before employees enter excavations greater than 4 feet (1.22 m) in depth. Open (g)(1)(i) 13 citations
(ii) Adequate precautions shall be taken to prevent employee exposure to atmospheres containing less than 19.5 percent oxygen and other hazardous atmospheres. These precautions include providing proper respiratory protection or ventilation in accordance with subparts D and E of this part respectively. 2 citations
(iii) Adequate precaution shall be taken such as providing ventilation, to prevent employee exposure to an atmosphere containing a concentration of a flammable gas in excess of 20 percent of the lower flammable limit of the gas. Open (g)(1)(iii)
(iv) When controls are used that are intended to reduce the level of atmospheric contaminants to acceptable levels, testing shall be conducted as often as necessary to ensure that the atmosphere remains safe. 1 citations
(2) Emergency rescue equipment. Open (g)(2) 3 citations
(i) Emergency rescue equipment, such as breathing apparatus, a safety harness and line, or a basket stretcher, shall be readily available where hazardous atmospheric conditions exist or may reasonably be expected to develop during work in an excavation. This equipment shall be attended when in use. Open (g)(2)(i) 3 citations
(ii) Employees entering bell-bottom pier holes, or other similar deep and confined footing excavations, shall wear a harness with a life-line securely attached to it. The lifeline shall be separate from any line used to handle materials, and shall be individually attended at all times while the employee wearing the lifeline is in the excavation. Open (g)(2)(ii)
Source: eCFR, text current as of 2026-10-15. Read all of 1926.651.
Where and how often it was cited
| Year | Citations |
|---|---|
| 2024 | 8 |
| 2025 | 8 |
| 2026 | 3 |
Top states: PA (3), NC (3), AR (2), AZ (2), TX (2)
Largest penalties
| Employer | Location | Penalty for this rule |
|---|---|---|
| 159103 - S. J. LOUIS CONSTRUCTION, INC. | ROXBORO, NC | $19,860 |
| 159654 - UNITED OF CAROLINAS, INC. | CHARLOTTE, NC | $4,965 |
| HORSESHOE CONSTRUCTION, INC. | ANDREWS, TX | $4,840 |
| LUIS ROLDAN | JONESBORO, AR | $4,839 |
| PERSANT CONSTRUCTION COMPANY, INC. | HOMESTEAD, FL | $4,052 |
Free toolbox talk
A 5-minute crew talk on 1926.651(g), plus alerts when this rule changes. Free.
OSHA interpretation letters
- Application of the Confined Spaces Advisor to construction; personal fall arrest system requirements. (2000-11-03)
- Review of Reeves Sleeve stretcher. (1993-06-24)
- Soil testing for excavations and confined spaces. (1992-06-15)
- Use of Cranes to Lift Personnel in Drilled Pier Operations (1992-01-28)
- Limitation on Enforcement of Certain Subsections of the Excavation Standard. (1990-08-01)
Related parts of this rule
- 1926.651(g)(1) Testing and controls 16 citations
- 1926.651(g)(1)(i) 13 citations
- 1926.651(g)(2)(i) 3 citations
- 1926.651(g)(2) Emergency rescue equipment 3 citations
- 1926.651(g)(2)(ii)
- 1926.651(g)(1)(iii)
Get your crew competent
Trainers on Black Belt Safety: Marc Harvey, Dana Reyes
Trainers and suppliers: feature your business on this rule for $25/month.
Frequently asked questions
When must the air in a trench be tested?
Before employees enter excavations greater than 4 feet deep where oxygen deficiency or a hazardous atmosphere exists or could reasonably be expected to exist.
What oxygen level is considered deficient?
Atmospheres containing less than 19.5 percent oxygen.
What rescue equipment is required?
Emergency rescue equipment, such as breathing apparatus, a safety harness and line, or a basket stretcher, must be readily available where hazardous atmospheres exist or may develop, and it must be attended when in use.
About this page
Sources
- 29 CFR 1926.651 (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.