Auxiliary heaters pose hazards on construction sites, including fire, carbon monoxide (CO) poisoning, and electrical shock. Fires can result from proximity to combustible materials or electrical overloading, while CO poisoning is a risk from unvented, fuel-burning heaters such as direct-fired “salamanders.” Electrical heaters used in damp areas can cause shocks, and workers may also be affected by injury or heat stress.
ISSUES:
Fire: Proximity to Combustibles – A primary cause of fires is placing heaters too close to flammable materials such as wood framing, tarpaulins, insulation, clothing, or debris. A clearance of at least 3 to 10 feet is typically required, depending on heater type and manufacturer specifications.
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Fire: Tipping Over – Unstable placement can cause heaters to tip over, potentially igniting surrounding materials.
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Fire: Fueling – Refueling units while hot or indoors can cause fires or explosions.
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Fire: Unattended Operation – Leaving heaters running unattended, especially during non-working hours, significantly increases fire risk.
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Carbon Monoxide (CO) Poisoning and Asphyxiation: Inadequate Ventilation
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Many temporary heaters use propane, natural gas, or kerosene, producing carbon monoxide, a colorless, odorless, and tasteless gas.
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Using direct-fired heaters that vent combustion products into enclosed or poorly ventilated spaces allows CO to accumulate to dangerous levels, displacing oxygen in the blood and potentially causing asphyxiation and death.
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Electrical Hazards: Overloaded Circuits – Electric heaters are high-wattage appliances. Hazards increase when using improper extension cords or power strips instead of plugging directly into a GFCI-protected outlet.
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Electrical Hazards: Shock and Fire
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Frayed cords, broken plugs, or damaged units pose a risk of electrical failure.
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Using electric heaters in damp or wet areas increases the risk of electrocution.
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Mold: Condensation – High humidity released by propane-fired heaters can lead to condensation and mold growth.
SOURCES OF HAZARDS:
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Not following manufacturer instructions
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Not providing proper ventilation
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Not using certified heaters for the application
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Not monitoring carbon monoxide
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Not securing heaters on level and plumb foundations
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Not storing fuel outdoors
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Not training employees on hazards and proper use
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Not having adequate fire extinguisher coverage
REGULATIONS: HEATERS
OSHA STANDARD 1926.153(g): Containers and regulating equipment installed outside buildings shall be upright on firm foundations or otherwise securely fastened. Flexible connections or special fittings shall guard against outlet piping movement due to settling.
OSHA STANDARD 1926.153(h)(13): For temporary heating, heaters (other than integral heater-container units) shall be located at least 6 feet from any LP-gas container. Blower and radiant-type heaters shall not be directed toward LP-gas containers within 20 feet.
OSHA STANDARD 1926.153(j): Storage of LPG containers within buildings is prohibited.
OSHA STANDARD 1926.153(k)(1): Outside storage distances for containers awaiting use:
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500 lbs. or less: 0 ft.
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501–6,000 lbs.: 10 ft.
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6,001–10,000 lbs.: 20 ft.
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Over 10,000 lbs.: 25 ft.
OSHA STANDARD 1926.153(l): Storage locations shall have at least one approved portable fire extinguisher rated not less than 20-B:C.
OSHA STANDARD 1926.154(a)(2): When heaters are used in confined spaces, sufficient ventilation shall be provided to ensure proper combustion, protect worker health, and limit temperature rise.
OSHA STANDARD 1926.154(b)(4): Heaters used near combustible tarpaulins, canvas, or similar coverings shall be located at least 10 feet away. Coverings shall be secured to prevent ignition or heater upset due to wind.
KEY POINTS:
Equipment that displaces oxygen presents serious risks, especially heaters.
HOW TO AVOID HEALTH AND SAFETY HAZARDS:
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Follow manufacturer guidelines for installation, operation, clearances, and maintenance.
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Provide adequate ventilation, especially for fuel-fired heaters. Never use direct-fired heaters in small, enclosed spaces.
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Use only certified heaters (UL, CSA, ETL) with safety features such as tip-over and overheat shut-offs.
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Keep combustibles at least 3 to 10 feet from heaters and maintain clear areas.
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Install carbon monoxide monitors where fuel-fired heaters are used.
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Place heaters on stable, level, non-combustible surfaces extending at least 2 feet beyond the unit.
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Store fuel tanks outdoors, secured upright, away from heat sources. Turn off gas supply when not in use.
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Use only approved and tested fuel regulation equipment.
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Maintain safe distances for fuel storage.
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Provide a minimum of 20 lb. ABC fire extinguishers.
DO’S FOR AUXILIARY HEAT:
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Use indirect heat whenever possible, preferably outdoor units.
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Place units on stable surfaces or solid ground.
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Ensure fuel line piping is flexible, AGA-rated, and protected from damage.
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Secure outdoor fuel storage and units with bollards or jersey barriers.
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Store extra fuel away from combustibles and structures.
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Inspect units, hoses, and tanks daily, and ensure scheduled inspections by qualified vendors.
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Require prior approval for subcontractors to use heaters on site.
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Conduct frequent inspections when heaters must remain on during non-working hours.
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Shut off and secure portable heaters when unattended.
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Notify the local fire department when temporary heating is used after work hours.
DON’TS FOR AUXILIARY HEAT:
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Don’t place heaters on non-combustible surfaces that do not extend at least four feet in front of the unit unless manufacturer-approved.
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Don’t use units that are not mechanically secured.
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Don’t allow clutter or poor material storage around heaters.
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Don’t use heaters without flame sensors or pilot safety valves.
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Don’t refuel hot units.
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Don’t refuel indoors or within 50 feet of buildings.
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Don’t operate heaters without CO detection, alarms, and make-up air systems.
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Don’t ignore symptoms of carbon monoxide poisoning such as dizziness, headache, chest pain, blurred vision, shortness of breath, or nausea.
