By: Thomas H. Welby Geoffrey S. Pope Published: July 2018

"Hot Work" Safety in Construction

Welding, cutting and brazing present a host of safety and health risks, including fire, explosion, toxic atmospheres, ultraviolet radiation, and electric shock.  If you work on sites where “hot work” is performed, you need to be familiar with the relevant standards, even if your employees perform no such work themselves.  Let’s look at the basics.

Moving, Transport, and Storage of Compressed Gas Cylinders:  Cylinder valves must be kept closed when work is not being performed, when the cylinders are empty, or they are being moved.

A chain, cylinder truck, or other steadying device should be used to keep cylinders from being knocked over while in use.  Cylinders should be secured in a vertical position, when being transported in a vehicle.  Regulators must be removed, and valve protection caps must be in place, before cylinders are moved.  Employees should never lift cylinders by their valve protection caps.

Cylinders should be kept a safe distance from welding operations, or behind fire-resistant shields.  They must not be placed in confined spaces, or where they might become part of an electrical circuit.

Cylinders, full or empty, must not be used as rollers or supports.

Use of Fuel Gas:  Before being connected to a regulator, a cylinder valve should be “cracked” (opened slightly and closed at once) by a person standing to the side of it.  Do not “crack” the valve where the gas would reach welding work, sparks, flame, or another source of ignition.

Cylinder valves should always be opened slowly, and those on fuel gas cylinders opened not more than 1-1/2 turns.  If a special wrench is required, it must be left in position, to allow the fuel gas flow to be shut off quickly.  In the case of manifolded or coupled cylinders, at least one such wrench shall be kept close by.  Nothing should be placed on top of a fuel gas cylinder that might damage the safety device, or impede the quick shutoff of the valve.

Fuel gas should be used through devices equipped with shutoff valves only if the pressure is reduced through a suitable regulator attached to the cylinder valve or manifold.  Before a regulator is removed from a cylinder valve, the valve must always be closed, and the gas released from the regulator.

If gas is found to be leaking from the valve stem, the valve shall be closed, and the gland nut tightened.  If that does not stop the leak, the cylinder must be taken out of use, tagged, and removed from the work area.

If fuel gas is leaking from the cylinder valve, and cannot be shut off, the cylinder should be properly tagged, and removed from the work area, except if a regulator attached to the cylinder valve will stop the leak through the valve seal.

If a leak should develop at a fuse plug or other safety device, the cylinder should be removed from the work area.

Fuel gas and oxygen manifolds:  Fuel gas and oxygen manifolds must bear the name of the substance they contain in letters at least 1” high, painted on the manifold, or on a sign permanently affixed to it.  The manifolds must be in safe, well-ventilated and accessible locations (never within enclosed spaces).

Oxygen and fuel gas hoses must not be used interchangeably, and a single hose having more than one gas passage must not be used.  Hose couplings must be of a type that cannot be unlocked or disconnected without a rotary motion.  Boxes used for the storage of gas hose should be ventilated, and hose must be inspected at the beginning of every shift, and removed from use if damaged or malfunctioning.

  Torches:  Torches must be inspected at the beginning of each shift for leaking shutoff valves, hose couplings and tip connections.  They may be lighted by friction lighters or other approved devices, but not by matches, or from hot work.

Regulators and Gauges:  Oxygen and fuel gas regulators and their gauges must be inspected regularly, and kept in good working order.

Oil and Grease Hazards:  Cylinders, cylinder caps, valves, couplings, regulators, hose and apparatus must be kept free from oil and greasy substances, and must not be handled with oily hands or gloves.

Welding Cables and Connectors:  Use only cable without repair or splices within 10 feet from the cable end to which the electrode holder is connected.  Cables with standard insulated connectors, or with splices having an insulating quality equal to that of the cable, are permitted.  Cables in need of repair must not be used.

Safe Operation of EquipmentAll equipment should be operated in a manner consistent with the manufacturer’s instructions.  OSHA requires that, when electrode holders are to be left unattended, the electrodes must be removed, and the holders placed or protected so that they cannot make electrical contact with employees or conducting objects.

When the cutter or arc welder has occasion to leave his work, or to stop work for any appreciable length of time, or when the arc welding or cutting machine is to be moved, the equipment’s power supply must be shut off.

Whenever practicable, arc welding and cutting operations are to be shielded by noncombustible or flameproof screens, as protection from the direct rays of the arc.

Naturally, faulty or defective equipment shall be reported to the supervisor, and taken out of service until repaired, or determined to be in good operating condition.

Ventilation and Protection:  Hot work operations involving toxic substances must not be performed without adequate ventilation.  Employees exposed to the same atmosphere must be protected in the same manner as the welders and burners themselves.

Mechanical ventilation can be either a “general mechanical ventilation system” or a “local exhaust system.”  General mechanical systems must produce the number of air changes necessary to maintain welding fumes and smoke within safe limits (as defined in subpart D of 29 CFR 1926).

Local exhaust ventilation consists of freely movable hoods, placed as close as practicable to the work.  Such ventilation must remove fumes and smoke, so as to keep concentrations within safe limits. 

Local exhaust ventilation or air line respirators are required, when hot work is to be performed in an enclosed space, and involves lead (other than as an impurity), metals coated with lead-bearing materials, cadmium, or mercury.  Both local exhaust ventilation and air line respirators are required, when the work involves beryllium-containing base or filler metals.

 Contaminated air from a workspace shall be exhausted into the open air, or otherwise clear of the intake air source.  All air replacing that which has been withdrawn must be clean and respirable.

Oxygen must not be used for ventilation, comfort cooling, blowing dust from clothing, or for cleaning work areas.

Confined spaces:  Generally, the foregoing ventilation requirements must be observed whenever hot work is done in a confined space.

By way of exception, if ventilation cannot be provided without blocking the means of access, employees in the confined space shall be protected by air line respirators, with an employee outside the confined space being assigned to maintain communication with those working inside it, and to provide assistance in case of an emergency.

When an employee must enter a confined space through a manhole or other small opening, means (e.g., safety belts and lifelines) must be used, and an attendant, with a pre-planned rescue procedure, stationed outside, to extricate the welder or cutter should the need arise.

Protective equipment:  Employees performing hot work, or working nearby, must wear suitable eye protective equipment.  All who are exposed to radiation must be covered completely, to prevent harm from ultraviolet rays.

Fire preventionArticles to undergo “hot work” must be moved to a designated location whenever practicable.  No hot work shall be done where the application of flammable paints, or the presence of other flammable compounds or dust concentrations, creates a hazard.

For more complete details concerning safety and health requirements for “hot work,” refer to Subpart J of 29 CFR 1926, and the publications and other OSHA standards referred to in the same.

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