An indirect fired heater burns its fuel outside the space and blows only clean dry air in through ducting, which is why it is the heater used in occupied buildings, for curing concrete and for drying finishes. Day rates run about $150 to $450 depending on output. A direct fired heater costs less and puts the combustion products, and all their moisture, into the room with you.
Indirect against direct fired
Direct fired heaters send the flame's output straight into the airstream. That is efficient, cheap to hire and fine for an open shell with air moving through it. Indirect units keep combustion behind a heat exchanger and vent it out of a flue, so the delivered air is dry and clean. Anything with people, paint or plaster in it wants the second kind.
Sizing the heater to the space
Work from the volume you are heating, how cold it is outside and how leaky the shell is. A tight thousand square foot room with normal ceilings is comfortable on the small end of the range. An open shell with the doors off needs far more, and it will still not hold temperature until somebody sheets the openings.
Fuel, ducting and the run time nobody budgets
These units drink diesel and run continuously overnight, so the fuel bill often passes the rental line by the second day. Ducting is hired by the length and adds resistance, which costs you delivered heat at the far end. Order the shortest sensible run, and ask what the tank holds at full output.
Where the flue and the intake go
The burner and its exhaust sit outdoors, upwind of any opening, and the flue must not discharge where the air intake or a doorway can draw it back in. Combustion products are a recognised hazard in construction air, which is exactly the risk an indirect unit is bought to avoid, so do not undo it with the placement.
Questions people ask about indirect heater rental
Can I run an indirect heater overnight unattended?
That is the normal use, and it is why the fuel tank size matters. The unit needs a fuel supply that lasts the night, a stable place to stand and a thermostat if you want it to cycle. Somebody should still check it in the evening and again first thing.
Will an indirect heater dry a slab?
It adds heat and moves dry air, which speeds the surface, but heat alone drives moisture out of the concrete and into the room air. Pairing the heater with a dehumidifier or with enough air changes is what actually removes it. Ask the yard for both on the same ticket.
How much power does one need?
The fuel does the heating but the blower and the controls still need electricity, usually a standard site supply for smaller units and a larger single or three phase feed for the big ones. If there is no power on the job yet, the heater and a generator get hired together.