---
title: "What are the maximum pressure and flammable mixture precautions required for oxygen-fuel gas welding under 29 CFR 1910.253? Answer in under 100 words."
canonical: https://www.m-i-n-d.ai/minds/welding/maximum-pressure-flammable-mixture-precautions-required-oxygen-fuel-gas-welding
jurisdiction: "US Federal · OSHA Standard 29 CFR 1910.253"
last_verified: 2026-08-26
license: CC BY 4.0 — https://creativecommons.org/licenses/by/4.0/
attribution: "Source: MIND (m-i-n-d.ai)"
---

# What are the maximum pressure and flammable mixture precautions required for oxygen-fuel gas welding under 29 CFR 1910.253? Answer in under 100 words.

Under 29 CFR 1910.253, mixtures of fuel gases and air or oxygen which may be explosive must be guarded against, and acetylene is not permitted at a pressure exceeding 15 psig (103 kPa gauge) or 30 psia (206 kPa absolute). No device allowing mixture of air or oxygen with flammable gases before consumption is allowed unless approved.

## Details / How it works

Per 29 CFR 1910.253(a)(1), any mixture of fuel gases with air or oxygen that may be explosive must be guarded against. No device that facilitates mixing these gases prior to consumption is permitted except at the burner or in a standard torch, unless the device has been approved for that purpose.

Per paragraph 1910.253(a)(2), under no condition may acetylene be generated, piped, or utilized at a pressure exceeding **15 psig** (103 kPa gauge pressure) or **30 psia** (206 kPa absolute). This limit also applies to use in pressurized chambers like caissons, underground excavations, or tunnel construction. The use of liquid acetylene is also prohibited.

## Numbers & thresholds

| Requirement | Limit |
|-------------|-------|
| Maximum acetylene pressure (gauge) | **15 psig** (103 kPa) |
| Maximum acetylene pressure (absolute) | **30 psia** (206 kPa) |
| **Note:** This does not apply to storage of dissolved acetylene in cylinders manufactured per DOT requirements, or to acetylene for chemical use. |

## Exceptions & edge cases

The 30 psia pressure limit is specifically intended to prevent unsafe use of acetylene in pressurized chambers such as caissons, underground excavations, or tunnel construction. However, this requirement does not apply to the storage of acetylene dissolved in a suitable solvent in cylinders manufactured and maintained according to U.S. Department of Transportation requirements, nor to acetylene intended for chemical use. The use of liquid acetylene is expressly prohibited in all cases.

## Sources

- [1] U.S. National Archives, Electronic Code of Federal Regulations — 29 CFR 1910.253 — Oxygen-fuel gas welding and cutting · https://www.ecfr.gov/current/title-29/section-1910.253 · as of 2026-08-26