Over here those are call a "Torpedo heater or a "Salamander" heater, after the the first commercial variant sold since the '40s or so. Those models were a deathtrap; they'd rattle apart, and the guts would set fire to anything they came in contact with. These are intended to warm large spaces, or even to warm open construction sites.
They are literally just a jet engine bolted to a fuel tank; they have a compressor section, a venturi section, and a fuel rail/ignition section, and they even run on the same fuel oil jet engines do.
What makes them a heater instead of a propulsion mechanism is the fact the venturi dead heads against the radiant cone; this causes a rolling effect in the airflow similar to how you blow a smoke ring. The air passes over the cone several times before it reaches escape velocity and is blown out around the perimeter.
None of these are what you can call safe; they are meant only as temporary heat in a well-ventilated area and never for unsupervised operation. The last couple decades have improved a lot, though... they're mandated to have a mechanical tip-over safety that shuts off fuel flow instantly if the unit even comes close to COG, and they now use a smart ignition system with a flame detector just as modern oil-fired furnace does, so it doesn't just keep pumping fuel if it doesn't ignite or if ignition fails.
Typically these things are good for 80-250K BTU as you'd buy from the local Homeowner Hell; but I've worked on sites with 850K BTU units bigger than a refrigerator.
As you might imagine, they tend to burn pretty sooty... any breathing problems whatsoever and they'll set you off.
mnem
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