The first time you run the heat each fall, a Leander house usually smells faintly of burning dust for a little while. That is normal, and it is not the furnace failing. What matters is how long it lasts and what it actually smells like, because a few smells mean stop using the system tonight rather than wait until morning.
The dust smell, and how long it should last
Your heat exchanger sits idle through a Central Texas summer and collects a fine layer of dust. The first time it heats up, that dust burns off. Carrier, whose factory authorized dealer network we belong to, describes this as usually temporary and harmless, and says the burning dust smell typically lasts anywhere from 30 minutes to a few hours after turning the heat on for the first time in the season.
So a faint dusty smell on the first evening is expected. The same smell three days later is not, and neither is a smell strong enough to make a room unpleasant to sit in. If it persists, Carrier's own guidance is to shut the system off, change the air filter, and call a professional if the odor remains.
The smells that mean stop
Three smells are different in kind, not degree. None of them are a wait-and-see.
- Burning plastic. Carrier notes this means more than dust burning off the heat exchanger, and can point to an overheated blower motor. Shut off the power to the system and call a technician.
- Something electrical, like hot wiring. This suggests an electrical fault in a component such as the blower. Stop using the furnace until it has been inspected.
- Rotten eggs or sulphur. That is the odorant added to natural gas. It likely indicates a gas leak and needs to be dealt with immediately, which means leaving and calling your gas utility from outside.
None of those are diagnosable from the thermostat, and none of them should be chased by opening up the equipment. Getting the cover off a furnace puts a homeowner next to a heat exchanger, a gas valve and line voltage at the same time.
The one you cannot smell at all
Carbon monoxide has no smell. The CDC describes it as an odorless, colorless gas that kills without warning, and reports that more than 400 Americans die each year from unintentional CO poisoning not linked to fires, with more than 100,000 emergency department visits. Early symptoms are headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion, which the CDC notes are commonly mistaken for the flu.
The EPA lists leaking chimneys and furnaces, back-drafting from furnaces, and gas water heaters among the household sources of CO, and attributes dangerous output to blocked or disconnected flues, flue leaks, poor maintenance and incorrect adjustment. That is the reason a heating system gets inspected rather than just filtered.
The Consumer Product Safety Commission's guidance on alarms is specific: install CO alarms with battery backup on every level of the home and outside sleeping areas, and not in kitchens or directly above fuel-burning appliances. If one sounds, move outside to fresh air and call 911. Do not go looking for the source and do not go back in until responders say so.
What to check before the first cold night
Three of these take a homeowner five minutes. The fourth does not.
- The filter. ENERGY STAR advises checking it monthly during heavy-use seasons and changing it at least every 3 months, or sooner if it looks dirty after a month, because a dirty filter slows airflow and makes the system work harder.
- Supply and return vents. Furniture moved for summer often ends up over a return. Restricted return air is one of the most common causes of a system that runs and runs without getting the house warm.
- Your CO alarms. Press the test button on each one. Replace batteries now rather than at 2am.
- A professional inspection. Both the CPSC and the EPA recommend having the heating system professionally inspected and serviced annually, including chimneys and flues checked for blockages, corrosion and loose connections.
Worth knowing what is at stake in the parts you cannot see: ENERGY STAR reports that sealing and insulating ducts can improve heating and cooling efficiency by as much as 20 percent, and that improper installation can reduce system efficiency by up to 30 percent. Those are duct and installation problems, not filter problems, and they do not announce themselves with a smell.
When to call us
Call the same evening for burning plastic, an electrical smell, a gas smell or a CO alarm. Book heating repair in the next day or two for a dust smell that has not cleared, a burner that will not light, or heat that never reaches temperature. If none of that is happening and you just want the system checked before winter, that is a maintenance visit, and early autumn is the right time for it.
Comfort Pros is a Carrier factory authorized dealer serving Leander, Cedar Park, Georgetown and Liberty Hill, licensed under TACL# TACLB116912E. Smells that turn out to be dust are the outcome we like. The point of looking is the small number of times it is not.