Welding, cutting, and hot work

Hot work is riveting, welding, flame cutting, or any other fire- or spark-producing operation. This is the definition provided in 1917.152(a).

• Examples of covered activities include oxy-fuel cutting, electric arc welding, brazing, torch heating, and any operation that produces sparks, slag, or open flame.
• If an operation produces sparks or heat that could start a fire, treat it as hot work under 1917.152(a).

No — hot work shall not be performed in a confined space until a designated person has tested the atmosphere and determined it is not hazardous. This requirement is in 1917.152(b).

• The designated person must verify there are no hazardous concentrations of flammable gases, vapors, toxic gases, or oxygen-deficient conditions before starting hot work.
• Where respiratory or other protective measures are required because of potential atmosphere hazards, follow OSHA's respiratory protection requirements such as 29 CFR 1910.134 as discussed in OSHA's "Oxygen-deficient atmospheres in HVAC" interpretation (https://www.osha.gov/laws-regs/standardinterpretations/2024-07-16).

When possible, hot work should be performed in designated locations that are free of fire hazards. This is stated in 1917.152(c)(1).

• Designated locations minimize the chance that sparks, slag, or heat will contact combustible materials.
• Establish and mark hot-work areas and keep them free of flammable/combustible materials per 1917.152(c)(1).

You must take all necessary precautions to confine heat, sparks, and slag so they cannot contact flammable or combustible material. This is required by 1917.152(c)(2).

• Use fire-resistant barriers, welding curtains, or covers to block sparks and hot slag.
• Remove or protect nearby combustibles, and isolate the work area to prevent ignition of adjacent materials in accordance with 1917.152(c)(2).

Suitable fire extinguishing equipment must be immediately available and maintained ready for use at all times. This is required by 1917.152(c)(3).

• Select extinguishers appropriate for the hazards (e.g., Class ABC or Class B for flammable liquids) and place them where workers can reach them quickly.
• Ensure extinguishers are inspected and employees know their location and basic use as part of hot-work preparations under 1917.152(c)(3).

When normal fire prevention precautions are not sufficient, additional personnel must be assigned to guard against fire during hot work and for a sufficient time afterward to ensure no fire hazard remains. This is required by 1917.152(c)(4).

• Those personnel must be instructed in potential fire hazards and in the use of firefighting equipment as part of their duties per 1917.152(c)(4).
• Typical practice: assign a fire watch during the work and continue surveillance for at least 30–60 minutes after completion (or longer if conditions warrant) to detect smoldering materials.

Drums and containers that contain or have contained flammable or combustible liquids must be kept closed and empty containers must be removed from the hot work area. These requirements are in 1917.152(c)(5) and 1917.152(c)(6).

• If you cannot remove a drum or container, follow 1917.152(c)(8) cleanup/ventilation steps (see next question).
• Close lids and caps to prevent vapors and keep containers away from the hot-work zone per 1917.152(c)(5).

They must be either filled with water or cleaned and then ventilated before hot work is performed. This is required by 1917.152(c)(8)(i) and the related provision in 1917.152(c)(8)(ii).

• "Cleaned" means removing residue and vapors to an extent that testing by a designated person shows the atmosphere is not hazardous, as required in 1917.152(c)(8)(ii).
• Before heating a drum or container, provide an opening to release built-up pressure during heat application per 1917.152(c)(8)(ii).

Hot work may be performed on such equipment only after a designated person has tested the atmosphere inside the equipment or tank and determined it is not hazardous. This is required by 1917.152(c)(7)(ii).

• The designated person must ensure no flammable vapors, gases, or dangerous oxygen-deficient or toxic atmospheres are present before work begins.
• Testing should be documented and repeated if the tank/equipment condition changes or work is interrupted, following 1917.152(c)(7)(ii).

No — hot work is not permitted in flammable or potentially flammable atmospheres. This prohibition is specified in 1917.152(c)(7)(i).

• If the atmosphere is potentially flammable, the atmosphere must be made safe (e.g., purged, ventilated, tested) before hot work may proceed under 1917.152(c)(7)(i).

Compressed gas cylinders must have valve protection caps in place except when in use, hooked up, or secured for movement, and they must be secured upright except when hoisted or carried. These and related requirements are in 1917.152(d)(1).

• Do not hoist cylinders by magnets, choker slings, or caps; hoist them on cradles or pallets as required by 1917.152(d)(1)(ii).
• Keep valves closed when cylinders are empty, being moved, or stored per 1917.152(d)(1)(vi).
• Do not expose cylinders to sparks, hot slag, or flame under 1917.152(d)(1)(x).

Oxygen cylinders must be separated from fuel gas cylinders and combustible materials by either a minimum distance of 20 feet or by a barrier having a 30-minute fire-resistance rating. This storage separation is required by 1917.152(d)(1)(xvi).

• If you cannot separate by 20 feet, use a certified 30-minute fire-resistant barrier between the oxygen and fuel gas cylinders per 1917.152(d)(1)(xvi).
• Keep cylinders upright and secured to prevent falling as required elsewhere in 1917.152(d)(1).

Cracking a cylinder valve means opening it slightly then closing it immediately to clear dust or dirt before attaching a regulator, but you must not crack valves if the gas could reach possible sources of ignition. This procedure is described in 1917.152(d)(2)(i).

• Crack valves away from ignition sources and only when it is safe to do so per 1917.152(d)(2)(i).
• If cracking could allow gas to reach sparks, flames, or hot surfaces, do not perform this step and instead use alternate safe procedures consistent with 1917.152(d)(2)(i).

Open cylinder valves slowly (no more than 1½ turns) and close valves and release gas from regulators before removing regulators. These practices are specified in 1917.152(d)(2)(ii) and 1917.152(d)(2)(iv).

• Keep an emergency shut-off wrench on the valve stem during use as required by 1917.152(d)(2)(ii).
• Close cylinder valves and bleed pressure from the regulator or manifold before removing the regulator to prevent sudden release of gas per 1917.152(d)(2)(iv).

If a leaking fuel gas cylinder valve can be stopped by tightening the gland nut, do so; if the leak continues, tag the cylinder, remove it from service, and move it to a safe location. If a plug or safety device leaks, tag and remove the cylinder from service and move it to a location where it will not be hazardous. These actions are required by 1917.152(d)(2)(v) and 1917.152(d)(2)(vi).

• A regulator may stop a leak temporarily, but a cylinder repaired must be tagged and not reused until fixed as described in 1917.152(d)(2)(vi).
• Tagging and removing defective equipment prevents accidental use per 1917.152(d)(2)(v).

Fuel gas and oxygen hoses must be easily distinguishable (by color or touch), not interchangeable, and must be inspected before use; hoses that have been subjected to flashback or show severe wear must be tested to twice the normal working pressure before reuse. These requirements appear in 1917.152(d)(3)(i) and 1917.152(d)(3)(iii).

• Never interchange oxygen and fuel hoses; use only specified hose types per 1917.152(d)(3)(i).
• If hose has been subjected to flashback, test at twice normal pressure (but not less than 200 psi) before reuse as required in 1917.152(d)(3)(iii).

Hose connections must be clamped or securely fastened to withstand twice the normal working pressure but not less than 300 p.s.i. This fastening requirement is in 1917.152(d)(3)(v).

• Use clamps or fittings rated for the pressure and check them regularly for wear.
• Ensure the connection method prevents leakage and separation under expected loads as required by 1917.152(d)(3)(v).

Torches must be inspected before each use for leaking shut-off valves, hose couplings, and tip connections, and torches must not be lighted with matches, cigarette lighters, other open flames, or from ongoing hot work. These rules are in 1917.152(d)(4)(ii) and 1917.152(d)(4)(iii).

• Use approved striker devices or built-in ignition systems to light torches rather than open flames per 1917.152(d)(4)(iii).
• Remove defective torches from service until repaired as required by 1917.152(d)(4)(ii).

Pressure regulators, including associated gauges, must be maintained in safe working order. This maintenance requirement appears in 1917.152(d)(5).

• Inspect regulators periodically for leaks, damage, and calibration; repair or replace defective units.
• Proper maintenance prevents overpressure or uncontrolled gas releases as required by 1917.152(d)(5).

The employer must ensure only manual electrode holders intended for arc welding and cutting that can handle the maximum current are used, and current-carrying parts that the user grips must be insulated to the maximum voltage to ground. These duties are in 1917.152(e)(1)(i) and 1917.152(e)(1)(ii).

• Use holders rated for the welding current to avoid overheating and failure per 1917.152(e)(1)(i).
• Ensure insulation protects the worker from shock under 1917.152(e)(1)(ii).

Welding cables must be insulated, flexible, and capable of handling the maximum current needed; the 10 feet nearest the electrode holder must be free of repairs or splices unless equivalent insulation is provided. These requirements are in 1917.152(e)(2)(i) and 1917.152(e)(2)(ii).

• If cable shows bare conductors, do not use that exposed portion until insulated equivalent to the original is applied per 1917.152(e)(2)(iii).
• Use insulated connectors equal in capacity to the cable as required by 1917.152(e)(2)(iv).

Ground return cables must have current-carrying capacity equal to or exceeding the welding unit's maximum output, and welding machine frames must be grounded either by a third wire or separate wire at the source. These requirements are in 1917.152(e)(3)(i) and 1917.152(e)(3)(v).

• Temporary ground return circuits (e.g., structures or pipelines) must have electrical contact at all joints and be rejected if arcs, sparks, or heat occur at any point per 1917.152(e)(3)(iii).
• Continuous ground return structures must be bonded and maintained to avoid electrolysis or fire hazards as required by 1917.152(e)(3)(iv).

When openings or cracks in flooring cannot be closed, precautions must be taken to ensure no employees or flammable materials below are exposed to sparks dropping through the floor; similar protections apply to cracks or holes in walls, open doorways, and broken windows. This is required by 1917.152(c)(6).

• Use fire blankets, screens, shields, or temporary covers to block falling sparks.
• Remove or protect combustibles on lower levels and assign a fire watch below the opening if necessary under 1917.152(c)(6).

Yes — hot work is generally prohibited near readily ignitable bulk materials like bulk sulfur unless suitable precautions are followed, the person in charge is knowledgeable, and the worker performing the hot work has been instructed in preventing and extinguishing sulfur fires, as stated in 1917.152(c)(7)(iii).

• Bulk sulfur is excluded from the blanket prohibition only when the stated special precautions, training, and knowledgeable supervision are in place per 1917.152(c)(7)(iii).
• Follow site-specific procedures to prevent ignition and ensure effective firefighting readiness around sulfur storage.

Before applying heat, an opening must be provided to release built-up pressure during heat application. This requirement is in 1917.152(c)(8)(ii).

• Failure to provide a vent can cause pressure buildup and rupture when heated; always vent and test the container atmosphere as required by 1917.152(c)(8)(ii).

Yes — structures or pipelines may be used as ground return circuits if they are not carrying gases or flammable liquids and if their current-carrying capacity equals or exceeds the welding unit's maximum output capacity, as stated in 1917.152(e)(3)(ii).

• Ensure continuous electrical contact at joints and that no arcing or heat is present; otherwise, the ground circuit is unacceptable per 1917.152(e)(3)(iii).
• Avoid using structures that contain flammable materials or gases as ground returns per 1917.152(e)(3)(ii).

Gas hose storage boxes must be ventilated. This storage requirement is in 1917.152(d)(3)(vi).

• Ventilation prevents accumulation of leaked gases in enclosed hose storage areas.
• Inspect storage boxes periodically to ensure vents are clear and functional per 1917.152(d)(3)(vi).

Cylinders must not be permitted to become part of electrical circuits or have electrodes struck against them to strike arcs, and they must not be used as rollers or supports. These prohibitions are in 1917.152(d)(1)(xi) and 1917.152(d)(1)(xii).

• Do not allow electrical current to pass through a cylinder or strike arcs against it, which could damage valves or cause heating per 1917.152(d)(1)(xi).
• Use proper rollers, cradles, or supports rather than cylinders to move or support loads per 1917.152(d)(1)(xii).

If a welding cable wears and exposes bare conductors, the exposed portion must not be used until it is protected by insulation equivalent in performance to the original cable insulation. This is required by 1917.152(e)(2)(iii).

• Tag out and remove damaged cable sections from service until properly repaired or replaced per 1917.152(e)(2)(iii).
• Use insulating sleeves or approved repair procedures that restore the cable's original protective qualities before reuse.

Grounding circuits must have low enough resistance so that enough fault current will flow to make the fuse or circuit breaker open the circuit. This requirement is stated in 1917.152(e)(3)(vi).

• Make sure grounding paths are continuous and sized so a protective device will trip in the event of a fault.

Ground connections must be mechanically and electrically adequate to carry the current involved. This is required by 1917.152(e)(4).

• Use secure clamps or bolted connectors and inspect connections regularly for corrosion, tightness, and continuity.

When electrode holders are left unattended, electrodes must be removed and holders placed to prevent employee injury. See 1917.152(e)(5).

• Place holders where they cannot contact conductive surfaces or start an arc; remove hot electrodes from holders and store safely.

The employer must ensure the power supply switch is kept in the off position when arc welders stop work or when machines are moved. This is required by 1917.152(e)(6).

• Turn off and, where appropriate, lock out power sources before relocating equipment or leaving a welding station.

No—arc welding or cutting equipment that has a functional defect must not be used. See 1917.152(e)(7).

• Remove defective equipment from service and repair it before reuse; document inspections and repairs as part of your safety program.

Arc welding and cutting operations must be separated from other operations by shields, screens, or curtains to block direct rays and sparks, and employees not protected by screening must wear appropriate filter lenses per paragraph (h). See 1917.152(e)(8)(i) and 1917.152(e)(8)(ii).

• Use non-reflective, flame-resistant screens sized to stop sparks and UV light.
• Where screening is impractical, provide and require filter lenses listed in 1917.152(h).

Welders exposed to their own arc or to each other's arc must wear filter lenses that meet the requirements of 1917.152(h), as required by 1917.152(e)(9).

• Select the appropriate shade number from the filter lens table in 1917.152(h).
• Ensure helmets and goggles fit properly and are free of reflective surfaces and leaks.

The control apparatus of arc welding machines must be enclosed except for operating wheels, levers, and handles. See 1917.152(e)(10).

• Enclosures help prevent accidental contact with live parts and reduce electric-shock and burn hazards.

Employees must use additional protection, such as rubber pads or boots, against electric shock when arc welding is performed in wet or high-humidity conditions. This is required by 1917.152(e)(11).

• Use dry insulating mats, rubber gloves, and remove standing water; inspect PPE for damage before use.

Employers must provide general mechanical ventilation or local exhaust systems that keep vapors, fumes, and smoke below hazardous levels and meet the listed requirements in paragraph (f)(1). See 1917.152(f)(1).

• General ventilation must maintain contaminants below hazardous levels (1917.152(f)(1)(i)).
• Local exhaust must use movable hoods close to the work to keep breathing-zone concentrations safe (1917.152(f)(1)(ii)).
• Exhaust air must be discharged clear of intake sources (1917.152(f)(1)(iii)).
• Replacement air must be clean and respirable (1917.152(f)(1)(iv)).
• Oxygen must not be used for ventilation, cooling, or cleaning (1917.152(f)(1)(v)).

When hot work is done in a confined space, the employer must provide either general mechanical or local exhaust ventilation, or require employees inside the space to wear supplied-air respirators with a standby person outside ready to communicate and provide emergency aid. See 1917.152(f)(2).

• If using supplied-air respirators, follow the respiratory requirements in 1910.134 and maintain a trained attendant outside the space.

For hot work in confined or enclosed spaces involving specific toxic metals, employers must provide the ventilation or respirators listed by metal group in [1917.152(f)(3)]. See 1917.152(f)(3)(i), 1917.152(f)(3)(ii), and 1917.152(f)(3)(iii).

• Lead-base metals, cadmium-bearing filler, and chromium-bearing metals require general mechanical or local exhaust ventilation (1917.152(f)(3)(i)).
• Zinc-bearing, certain lead-containing, cadmium-bearing/coated, and mercury-coated metals require local exhaust ventilation or supplied-air respirators (1917.152(f)(3)(ii)).
• Beryllium-containing metals require local exhaust ventilation plus supplied-air respirators or self-contained breathing apparatus per 1910.134 (1917.152(f)(3)(iii)).

For open-air hot work involving the listed toxic metals, employees must be protected by respirators per [1910.134] (and for beryllium, by supplied-air respirators), and anyone exposed to the same atmosphere must have the same respiratory and protective equipment as the welder. See 1917.152(f)(3)(iv) and 1917.152(f)(3)(v).

• Follow the respiratory program requirements in 1910.134.
• Evaluate exposure and provide the same class of protection to bystanders working in the same contaminated atmosphere.

Inert-gas metal-arc welding requires several specific precautions: keep chlorinated solvents at least 200 feet away from the arc, use proper filter lenses or screening, fully cover exposed skin to prevent UV burns, ensure helmets and hand shields do not leak or reflect, and protect employees during stainless steel welding with local exhaust or supplied-air respirators. See 1917.152(f)(4)(i)-(iv).

• Do not weld on surfaces recently cleaned with chlorinated solvents unless thoroughly dry (1917.152(f)(4)(i)).
• Use shields or filter lenses complying with 1917.152(h).

Before hot work on surfaces with preservative coatings of unknown flammability, a designated person must test the coating to determine its flammability. This is required by 1917.152(g)(1).

• If scrapings burn extremely rapidly, treat the coating as highly flammable (1917.152(g)(2)).
• Highly flammable coatings must be stripped, and an uncoiled fire hose with fog nozzle under pressure must be immediately available (1917.152(g)(2)).
• Alternatively, strip at least 4 inches around the heat area or provide supplied-air respirators per 1910.134 (1917.152(g)(3)).

Choose a filter lens with the shade number appropriate for the operation using the values listed in Table G-1 of 1917.152(h); small variations by 1–2 shade numbers are allowed for personal preference. See 1917.152(h)(2).

• If you wear filter lenses in goggles under a helmet, the combined shade must equal the value shown in Table G-1 (1917.152(h)(3)).
• Inspect lenses for cracks and cleanliness before each use.

For Shielded Metal-Arc Welding with 1/16- to 5/32-inch electrodes, use filter lenses with shade number 10 per Table G-1 in 1917.152(h).

• If you choose goggles under a helmet, make sure the combined shade equals the Table G-1 value (1917.152(h)(3)).

Exhaust from working spaces must be discharged into the open air clear of intake air sources, and replacement air must be clean and respirable, as required by 1917.152(f)(1)(iii) and 1917.152(f)(1)(iv).

• Design ventilation to avoid recirculation of contaminated exhaust back into the workspace; ensure makeup air is from a clean source.

When hot work in confined spaces requires supplied-air respirators, employers must follow the respirator requirements in [1910.134], and 1917.152(f)(2) explains that supplied-air respirators may be required with an outside standby. See 1917.152(f)(2) and 1910.134 for the detailed respirator program rules.

• Implement fit testing, training, maintenance, and medical evaluation per 1910.134.

An oxygen-deficient atmosphere is defined in [1910.134] as an atmosphere with oxygen content below 19.5% by volume, and that definition is the basis for respirator and IDLH considerations referenced in [1917.152(f)(2)]. See 1910.134 and the OSHA interpretation memorandum on oxygen-deficient atmospheres at https://www.osha.gov/laws-regs/standardinterpretations/2024-07-16.

• When confined-space oxygen falls below 19.5%, treat the atmosphere as IDLH and follow the supplied-air or SCBA requirements and attendant procedures in [1910.134].