1910.426: Mixed-Gas Diving
Employers doing mixed-gas diving may dive only when a decompression chamber is ready at the dive location, with bells or closed bells required at the depths and decompression times set in the rule. Each diver must be tended, a standby diver must be available, and each operation must have a primary breathing gas supply for the full planned dive and a dive-location reserve supply.
Key takeaways
- 1910.426 is part of OSHA's general industry standards (29 CFR Part 1910, Subpart T).
- OSHA cited it 3 times in the last 3 years, in 2 inspections, with $14,187 in current penalties.
- 1 death is linked to inspections that cited this rule.
- Most-cited part: 1910.426(c) Procedures (2 citations).
- Free 5-minute toolbox talk for your crew below.
In this article
What this rule covers
29 CFR 1910.426, "Mixed-gas diving", is an OSHA general industry standard (Part 1910, Subpart T). It has 19 numbered 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
Show the full text of 1910.426 (19 paragraphs)
(a) General. Employers engaged in mixed-gas diving shall comply with the following requirements, unless otherwise specified.
(b) Limits. Mixed-gas diving shall be conducted only when: 1 citations
(1) A decompression chamber is ready for use at the dive location; and 1 citations
(i) A bell is used at depths greater than 220 fsw or when the dive involves inwater decompression time of greater than 120 minutes, except when heavy gear is worn or when diving in physically confining spaces; or
(ii) A closed bell is used at depths greater than 300 fsw, except when diving is conducted in physically confining spaces.
(c) Procedures. Open (c) 2 citations
(1) A separate dive team member shall tend each diver in the water. Open (c)(1) 1 citations
(2) A standby diver shall be available while a diver is in the water. Open (c)(2) 1 citations
(3) A diver shall be stationed at the underwater point of entry when diving is conducted in enclosed or physically confining spaces.
(4) Each diving operation shall have a primary breathing gas supply sufficient to support divers for the duration of the planned dive including decompression.
(5) Each diving operation shall have a dive-location reserve breathing gas supply.
(6) When heavy gear is worn:
(i) An extra breathing gas hose capable of supplying breathing gas to the diver in the water shall be available to the standby diver; and
(ii) An inwater stage shall be provided to divers in the water.
(7) An inwater stage shall be provided for divers without access to a bell for dives deeper than 100 fsw or outside the no-decompression limits.
(8) When a closed bell is used, one dive team member in the bell shall be available and tend the diver in the water.
(9) Except when heavy gear is worn or where physical space does not permit, a diver-carried reserve breathing gas supply shall be provided for each diver:
(i) Diving deeper than 100 fsw or outside the no-decompression limits; or
(ii) Prevented by the configuration of the dive area from directly ascending to the surface.
Source: eCFR, text current as of 2026-10-15.
Injuries linked to this rule
1 death is linked to inspections where OSHA cited 1910.426.
At 3:18 p.m. on October 2, 2024, Employee #1, employed as a shellfish fishing diver near Sisters Island, was diving for Geoducks in an area experiencing strong tides and rough seas. After starting his second dive of the day, Employee#1 radioed the tender aboard the…
Where and how often it was cited
Free toolbox talk
A 5-minute crew talk on 1910.426, plus alerts when this rule changes. Free.
OSHA interpretation letters
None exist. OSHA has not published a letter of interpretation for 1910.426.
Most-cited parts of this rule
- 1910.426(c) Procedures 2 citations
- 1910.426(c)(1) 1 citations
- 1910.426(c)(2) 1 citations
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Frequently asked questions
When is a bell required?
At depths greater than 220 fsw or when inwater decompression time is greater than 120 minutes, except when heavy gear is worn or in physically confining spaces.
When is a closed bell required?
At depths greater than 300 fsw, except when diving in physically confining spaces.
What breathing gas supplies are needed?
A primary supply sufficient for the planned dive including decompression, and a dive-location reserve supply.
About this page
Sources
- 29 CFR 1910.426 (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.