Before selecting and turning on a heater, make sure the location is appropriate for heater use. Always keep a charged, inspected, ready-for-use fire extinguisher on hand.
There are two basic styles of heaters: forced air and convection. Forced air heaters have a powerful fan that draws air in and then though the heater. These heaters must be used in areas with plenty of fresh air and should be placed carefully in an area free of dirt and clutter because they get very hot.
Convection heaters use natural air movement to heat air as it moves through the heater. No fan is used. These units get very hot, too. They can be used indoors, but there must be a constant supply of fresh air and at least a 36” clearance all around from any combustible material.
Heaters can be fueled by electricity, propane, natural gas or liquids such as Number 1 fuel oil or kerosene.
Electric: Electric heaters are not as common on construction sites as fuel- or gas-fired heaters. An electric heater should be used where heated air must be free of combustion byproducts (like fumes, carbon monoxide and carbon dioxide). An electric heater is useful in a closed space where the supply of fresh air is limited (like a jobsite office trailer).
Liquid Fuel: Liquid fuel heaters typically burn oil and kerosene and are a good source of heat, but they do, however, require ample fresh air ventilation and a constant supply of fuel to refill the heaters.
Some liquid-fueled heaters release exhaust fumes with an oily smell, which can be irritating for workers. It is possible to vent the heater to the outdoors and produce a large volume of heated air free of combustion byproducts. These heaters are sometimes used to heat the air over a new concrete placement in winter.
Propane (LPG)/Natural Gas (LNG): Propane- or natural-gas heaters are lightweight and easy to transport. Both gases are highly flammable and explosive. Use the necessary precautions when handling, storing and using these gases.
Propane is heavier than air. Leaking gas will settle in low-lying areas such as basements and trenches. This can lead to asphyxiation and explosion. Keep propane containers and tanks secured and upright at all times. Natural gas is lighter than air and, if leaking, will rise to the ceiling of an enclosed space. If you smell gas, turn off the heater and do not use it (or any other heater) until you find and repair the source of the leak.
The next time you need to use a portable heater, don’t just grab the first one you see. Think about where it will be used and select the correct heater for the job.