Exothermic Cutting & Thermal Lances

Exothermic cutting uses a tube or rod that burns in a stream of oxygen at extreme temperatures to cut through steel, cast iron, concrete, rock, scrap and even underwater structures. It is a powerful tool for demolition, salvage and emergency work. It is also a fire, burn and fume hazard, and it creates streams of molten slag that can travel far.

• Demolition & Salvage Crews
• Steel Mill & Foundry Workers
• Underwater & Marine Cutters
• Welders & Fabricators

What these tools are

• Exothermic cutting rods (burning bars): tubular rods packed with metal wires or elements that burn when oxygen flows through them. A torch handle holds the rod and connects to an oxygen supply. The rod ignites with an arc, a spark or a flame and then burns itself like a fuse, reaching temperatures of several thousand degrees.
• Thermal lances (oxygen lances) use a steel pipe filled with rods or wires and fed with oxygen, to cut very thick metal and concrete, and to clear furnace taps and blockages.
• Oxygen supply: cylinders, regulators and hoses at high pressure. See Oxygen Hazards and Oxy-Fuel Setup.
• These tools are used without fuel gas but they are still hot work, covered by OSHA's welding and cutting rules and company hot work programs. See Welding & Cutting and Hot Work Permits.

Main hazards

• Extreme heat and burns: the rod and nozzle reach temperatures far higher than ordinary torches, and the work piece and surroundings become dangerously hot. See Burn First Aid.
• Molten slag and sparks: they can fly or flow a long way, igniting combustibles, falling through floors and gaps, and burning workers below. See Sparks & Fire Risk.
• Oxygen fires: oxygen enrichment makes clothing, oil, grease and rubber ignite easily. Hoses and regulators in contact with oil can explode. See Oxygen Hazards.
• Flashback, backfire and equipment failure: the rod may burn back into the handle, hoses can burn through, and cylinders can overheat. See Flashback Arrestors.
• Fumes and dust: metal oxide fumes from cutting and silica from concrete and refractory. Coatings such as paint and galvanizing add toxic fumes. See Galvanized Metal Fume Fever and Silica.
• Explosion hazards: cutting closed containers, tanks, drums and pipes that held flammable materials; trapped water or moisture in concrete can burst and throw fragments. See Hot Work on Drums & Tanks.
• Light and noise: intense glare and loud burning. See Welding Helmets.
• Structural collapse when cutting supports or loaded members. See Demolition.

Before cutting

• Get a hot work permit and follow your program: inspect the area, remove or protect combustibles within 35 feet where required, cover openings that sparks could fall through, and arrange a fire watch during and for at least 30 minutes after cutting (longer where the program requires). See Hot Work Permits and Hot Work in Occupied Buildings.
• Check the material: don't cut containers, pipes or equipment unless you know it's empty, cleaned, purged and tested. Look for pressure, residues and coatings. See Inerting & Purging.
• Plan where slag will go and what's underneath, including floors below, other workers and equipment. Use fire-resistant blankets, shields and barricades. See Fire Blankets.
• Inspect oxygen equipment: cylinders, regulators, hoses and fittings must be clean, oil- and grease-free and in good condition, with correct pressure settings for the rod. Use equipment and hoses rated for oxygen service. Leak test with approved solution, not oil.
• Make sure ventilation or respiratory protection is adequate for fumes and dust. See Respiratory Protection.
• Know the emergency plan, including extinguishers, first aid and how to shut off oxygen quickly.

During cutting

• Wear flame-resistant clothing, leather gloves, leather boots, a welding helmet or face shield with the right shade and a hood or leather cape, hearing protection and a respirator as needed. No synthetic or oily clothing. See Flame-Resistant Clothing and Welding Leathers.
• Follow the maker's instructions for lighting the rod, oxygen pressure, rod handling and safe angle. Hold the torch away from your body, stay out of the slag path and keep your free hand clear.
• Keep everyone else back, with barricades and warnings, and use shields to protect people nearby.
• Don't use water on burning rods or hot work areas except as the procedure says, since steam and molten metal can explode. Keep the rod stub out of puddles and moisture when working on wet surfaces.
• Don't cut concrete or rock without understanding the risk of spalling and explosive fragments, and wear a face shield and protective clothing. Check for rebar, utilities and structural supports.
• If a rod flares back or the handle gets hot, shut off oxygen at the cylinder and set the torch in a safe place.
• Handle spent rod stubs as hot waste: drop them in a metal bucket or designated container away from combustibles.

After cutting and storage

• Keep the fire watch in place and inspect hidden areas, behind walls and below, for smoldering. See Fire Prevention.
• Shut off the oxygen cylinder valve, bleed the regulator and hoses and store cylinders upright and secured, away from oil, heat and flammable gases. See Compressed Gas Cylinders.
• Store rods dry and protected, following the maker's instructions, and don't leave them in hot vehicles. Keep them away from ignition sources.
• Clean up slag and debris, and dispose of waste properly. Allow cut metal to cool before handling.
• Document the permit closeout and any problems for review.

Exothermic cutting checklist

• The hot work permit, fire watch and slag controls are in place
• The item to be cut is known to be empty, cleaned and safe to cut
• Oxygen equipment is oil-free, inspected and leak tested
• I wear FR clothing, leathers, face and hearing protection and a respirator if needed
• Spent rods are placed in metal containers, and oxygen is shut off and bled at the end

Last updated: October 5, 2026