Learn the ventilation, respirator, attendant, toxic-metal and fire-prevention rules that apply when you weld, cut or heat inside a confined space on a construction site.
Based on OSHA 29 CFR 1926.353 and 29 CFR 1926.352 (construction) · about 5 min read
Need proof of training? The full course (25 min) adds practice questions, a job scenario, the final quiz and a certificate your employer can verify.
Whenever you weld, cut or heat in a confined space, either general mechanical ventilation or local exhaust ventilation must be provided. Two narrow exceptions are covered later in this course: when ventilation cannot be obtained without blocking the way out, and for some metals of toxic significance.
General mechanical ventilationEnough capacity, arranged to produce the number of air changes needed to keep welding fumes and smoke within safe limits.
Local exhaust ventilationFreely movable hoods that you or the burner place as close as practicable to the work, to remove fumes and smoke at the source and keep the breathing zone within safe limits.
Sometimes getting enough ventilation would block the way in and out. When sufficient ventilation cannot be obtained without blocking the means of access:
Employees in the confined space are protected by air line respirators.
An employee on the outside is assigned to maintain communication with those working inside and to aid them in an emergency.
Reference: 29 CFR 1926.353(b)(2)
Respirators, attendant and rescue
Small openings: quick removal and an attendant
If a welder must enter a confined space through a manhole or other small opening:
Means must be provided for quickly removing the welder in an emergency.
If safety belts and lifelines are used for this purpose, they must be attached to the welder's body so the body cannot be jammed in a small exit opening.
An attendant with a pre-planned rescue procedure is stationed outside to observe the welder at all times and be capable of putting rescue operations into effect.
Reference: 29 CFR 1926.353(b)(3)
Metals of toxic significance
Zinc, cadmium filler and chromium
Some metals are of toxic significance when they are welded, cut or heated. Hot work in any enclosed space involving the metals in this group must be done with either general mechanical or local exhaust ventilation. For example:
Zinc-bearing base or filler metals, or metals coated with zinc-bearing materials
Cadmium-bearing filler materials
Chromium-bearing metals, or metals coated with chromium-bearing materials
For this more dangerous group, general ventilation is not enough. Work in any enclosed space must be done with local exhaust ventilation, or employees must be protected by air line respirators:
Metals containing lead, other than as an impurity, or metals coated with lead-bearing materials
Cadmium-bearing or cadmium-coated base metals
Metals coated with mercury-bearing metals
Beryllium-containing base or filler metals: because of its high toxicity, both local exhaust ventilation and air line respirators
Doing these operations in the open air: employees are protected by filter-type respirators. The exception is beryllium-containing base or filler metals, where air line respirators are required.
Other employees exposed to the same atmosphere as the welders or burners must be protected in the same manner as the welder or burner.
When practical, move the object to a designated safe location. If it cannot be readily moved, all movable fire hazards in the vicinity are taken to a safe place or otherwise protected.
No hot work where flammable paints, other flammable compounds or heavy dust concentrations create a hazard.
Fire extinguishing equipment must be immediately available in the work area and kept ready for instant use.
When normal precautions are not sufficient, additional personnel are assigned to guard against fire during the work and for a sufficient period after it to ensure no possibility of fire exists. They must be instructed on the specific anticipated fire hazards and how the firefighting equipment is to be used.
Gas can leak through a leaking or improperly closed torch valve and build up in an enclosed space. So:
The gas supply to the torch is positively shut off at some point outside the enclosed space whenever the torch is not to be used, or is left unattended for a substantial period, such as during the lunch period.
Overnight and at the change of shifts, the torch and hose are removed from the confined space.
Open end fuel gas and oxygen hoses are removed from enclosed spaces immediately when they are disconnected from the torch or other gas-consuming device.
Reference: 29 CFR 1926.352(g)
Fire prevention
Drums, containers and hollow structures
Drums, containers or hollow structures that have contained toxic or flammable substances must, before hot work, either be filled with water or be thoroughly cleaned of such substances, ventilated and tested.
Before heat is applied to a drum, container or hollow structure, a vent or opening must be provided for the release of any built-up pressure.
Fact-checked against the regulation text on October 09, 2026. This certificate records completion of awareness training based on OSHA 29 CFR 1926.352(a), (c), (d), (e), (g), (i) and (j) and 29 CFR 1926.353(a), (b) and (c). It is not an OSHA card or license, and it does not by itself meet the instruction requirement of 29 CFR 1926.352(e). Section 1926.353 has no worker training paragraph of its own. Your employer must still instruct any additional personnel assigned to guard against fire as to the specific anticipated fire hazards and how the firefighting equipment provided is to be used, and, where air line or filter-type respirators are required, protect employees with respirators in accordance with the requirements of subpart E of Part 1926.
This guide explains the rule in plain words. Always read the regulation itself and your employer's site-specific procedures.