Homeowner Guide

Is That Furnace Smell or Noise Something to Worry About?

Furnaces make more noise and produce more smell right after they've been off all summer than they will once they've run a few cycles. Most of what homeowners notice in the first week of the heating season in Michigan is normal. Some is not — and knowing the difference matters for safety, not just comfort.

Usually Normal

These are common and typically not a safety concern:

• A faint dusty or 'burning' smell for the first several minutes the first time the furnace runs each season — this is dust burning off the heat exchanger and clears on its own
• A metallic ticking or popping sound as ductwork and metal furnace components heat up and expand
• A brief mechanical hum or whir when the blower motor or draft inducer starts up
• A musty smell if the furnace or ducts have been closed up and slightly damp — often resolves once air has circulated for a while

Treat These as a Safety Issue

Some smells and sounds are not routine and should be treated seriously. A rotten-egg smell (natural gas has an odorant added specifically so leaks are noticeable) or any hissing sound near the gas line or furnace means you should leave the house immediately, avoid operating light switches or anything electrical on your way out, and call your gas utility's emergency line from a safe location before calling us or anyone else. A persistent burning-plastic or electrical smell that doesn't fade after a few minutes can indicate an overheating component and is worth shutting the furnace off and calling for service. Loud banging (as opposed to light ticking) can indicate a cracked heat exchanger or delayed ignition — both are worth a prompt inspection rather than waiting.