Not every cold house is a boiler emergency, and the triage exists to tell the difference fast. The first split is which rooms are cold: whole house going cold points at the boiler or the fuel; only the far bedrooms cold while the living areas hold temperature points at distribution — the ranch long-run problem — which is urgent for comfort but not a freeze emergency. The second split is fuel: on oil, the tank gauge reading decides whether this is a delivery-plus-reprime or a burner fault, and those are different dispatches. The third is trajectory: a house at 64 and steady can wait for morning; a house at 55 and falling cannot.
Have these ready and the call takes minutes: fuel type, tank gauge if oil, any error code or the state of the red reset button, which rooms are cold, and how fast the indoor temperature is dropping. “Oil, gauge reads empty, reset button lit, whole ranch at 58 and falling, 11590” is a complete triage in one sentence. Renters should say so too — the owner usually authorizes heating work, and the triage says that upfront instead of after a truck rolls.