An indirect fired heater burns its fuel in a sealed chamber and sends the combustion gases out through a flue, so only clean dry warm air reaches the space. Hire runs from about $250 a week for a 200,000 BTU unit to $1,200 and above for a million BTU trailer machine, with fuel, ducting and a power supply as separate lines.
Indirect against direct, and why the choice matters
A direct fired heater sends everything it produces into the space, including water vapour and combustion products, so it needs generous ventilation and suits open shells and thawing ground. An indirect unit keeps the exhaust separate. That is what makes it the one for occupied areas, drying work, painting, plastering and anywhere added moisture would undo the job.
Sizing is BTU against volume and air changes
Work out the cubic volume of the space, how leaky it is and how far you need to raise the temperature, then let the yard convert that to BTU. Rental fleets typically step through 200,000, 400,000, 700,000 and a million BTU. Two smaller units ducted to opposite ends of a building usually beat one large one in the middle.
Fuel, power and what the yard actually delivers
Most units burn diesel or kerosene and also need mains or generator power for the blower and controls. Small machines carry an integral tank measured in hours of run time; larger trailer heaters are fed from a separate diesel tank hired alongside. Confirm who supplies fuel and who returns the machine full.
Ducting is where the heat is won or lost
Rented heaters push air through flexible duct, and every metre, bend and crushed section costs delivered temperature. Hire the duct with the machine so the diameters match, run it as straight as the building allows, and put the outlets where the work is. Give the return air somewhere to come from, or the unit fights itself.
Questions people ask about indirect fired heater rentals
Can an indirect fired heater run inside an occupied building?
That is what it is designed for, provided the flue is properly routed outside and the manufacturer's clearances are respected. The heater itself normally sits outside with only ducting entering the space. Direct fired units in the same situation demand ventilation that defeats the point of heating.
How much diesel does a rented heater use?
Roughly in proportion to output, so a 400,000 BTU unit at full fire gets through several gallons an hour and a million BTU machine considerably more. Ask the yard for the burn rate at high and low fire, then size the fuel tank so nobody is refilling it in the middle of the night.
Is an indirect heater the right choice for drying a slab?
For warmth without added moisture, yes, and it is the standard hire for winter concrete work and for drying out a building. Pair it with air movers, and with a dehumidifier if the space is closed, because heating alone raises the air's capacity to hold water without removing any of it.