Tar Kettles & Hot Asphalt

Roofing kettles and tar pots heat asphalt to several hundred degrees so it can be mopped or poured on roofs. Hot asphalt sticks to skin and causes deep, severe burns. It can also catch fire or erupt if water gets in. Careful setup, steady temperature control and the right PPE are essential.

• Roofing
• Paving
• Construction

Hazards

• Severe burns: asphalt used in roofing is often heated to about 350°F to 500°F. It clings to skin, continues to burn and is hard to remove. Even small splashes cause serious injury.
• Water and boil-over: a little water in hot asphalt turns to steam instantly and can throw hot material out of the kettle. Wet or damp materials, rain and condensation are dangerous.
• Overheating and fire: asphalt can ignite if it’s overheated past its flash point, and vapors can catch fire. A kettle fire can spread to the roof, the building or the truck.
• Fuel gas: kettles are often fired with propane or other fuels, which can leak or explode. See Propane and Compressed Gas Cylinders.
• Fumes: asphalt fumes irritate the eyes, nose and throat, and long exposure raises health concerns. See Ventilation and Solvents.
• Falls, spills and tipping: carrying hot buckets on a roof, or setting the kettle on an unstable surface.

Kettle setup

• Place the kettle on level, firm ground, away from buildings, overhead lines, trees and combustible material. Don’t put kettles on roofs unless they are designed and approved for it. Follow your employer’s plan, the maker’s instructions and local fire rules.
• Set the kettle so that wheels are chocked and the unit is stable, and no one is downwind of fumes or standing under the discharge.
• Make sure the kettle has a working thermometer, a lid, a safe way to shut off the burner, and automatic temperature controls where the unit is equipped with them. Don’t use a kettle with a broken thermometer.
• Keep at least one fire extinguisher of the right type (a dry chemical type rated for flammable liquids) within reach. Know that water must never be used on an asphalt fire. See Fire Extinguishers (PASS).
• Keep the area around the kettle clear of rags, paper and flammable materials. Don’t store extra fuel nearby.
• Position the kettle so that if it leaks or spills, the asphalt won’t flow toward people, drains or buildings.

Heating and loading

• Heat slowly and evenly. Follow the asphalt maker’s temperature guidance, and use the thermometer. Don’t exceed the flash point or the maximum temperature the manufacturer lists.
• Don’t overfill. Leave room for expansion and for adding material. Many manuals say not to fill more than about two thirds.
• Load carefully: never drop wet or frozen asphalt, or damp blocks, into hot liquid. Water and ice trapped in a block cause a violent reaction. Warm blocks near the kettle to dry them, and slide them in gently at the edge, not from above. Use a ladle or tool, not your hands.
• Keep water, wet tools, and snow and ice out of the kettle. Cover the kettle in rain.
• Stir only with dry tools. Stand upwind and behind a shield or lid.
• Never leave a kettle burning unattended.
• Turn off the burner and let the kettle cool before moving it or cleaning it. Don’t tow a hot kettle on a public road unless it is designed and approved for it.

Fuel and fire safety

• Check propane hoses, regulators and connections for leaks with soapy water, not a flame. See Propane.
• Keep cylinders upright, secured and away from the burner and hot surfaces. Follow your local fire rules for distance.
• Shut off the fuel before refilling or changing cylinders. No smoking near the kettle or fuel.
• If the asphalt catches fire in the kettle, shut off the burner and fuel, close the lid to smother the fire, and use a dry chemical extinguisher. Never throw water on it. Call 911 for any fire you can’t control. See Jobsite Fire Prevention.
• Know that hot work, torches and open flames on the same roof add risk. See Torch-Applied Roofing and Hot Work Permits.

Moving hot asphalt

• Use enclosed pumps, insulated pipes, hoses or mechanical hoists and buckets to move asphalt rather than carrying open pails. Keep hoses in good condition, and release pressure before disconnecting.
• If you must carry hot asphalt, use covered, properly rated buckets, filled only partway, with secure handles. Don’t carry them on ladders. Use hoists and rope lines for lifting.
• Clear the area below when hoisting, and use barricades and signs. See Roofing and Roof Work.
• Keep walking surfaces clear of drips and spills, which are slippery and hot.
• Pour with controlled motion, and keep your body away from splash zones.

PPE and first aid

• Wear long sleeves and long pants made of natural fibers (cotton or wool), not synthetics that melt. Wear leather work boots with no seams that trap asphalt, cuffless pants over boots, and heat-resistant gloves with cuffs.
• Wear safety glasses with side shields and a face shield when pouring or working near the kettle. See Eye & Face Protection and Hand Protection.
• Use respiratory protection if required by the exposure assessment. See Respiratory Protection.
• For an asphalt burn, cool the area with cool running water immediately, and keep cooling. Don’t try to peel or scrape off the asphalt. Cover loosely, and get emergency help. Remove jewelry and clothing that isn’t stuck. See Burn First Aid.
• Keep a first aid kit and clean water at the site.

Kettle checklist

• Kettle on stable ground, away from buildings, lines and combustibles
• Thermometer and controls working; lid and shutoffs available
• Dry chemical extinguisher at hand; no water near the kettle
• Asphalt heated slowly, not overfilled; no wet or frozen material added
• Propane connections leak-tested; cylinders secured
• Hot asphalt moved by pump or hoist where possible; area below cleared
• Long sleeves, face shield, gloves and boots on; burn first aid understood

Last updated: October 4, 2026