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Furnace Odor

We just had our furnace serviced (just routine). The only problem the technician found was the float in the humidifier which he replaced. Ever since then there has been an odor that smells kind of like melting plastic?? I have had the company back to check and they couldn't find anything?? My husband can't smell it, but my sense of smell is very acute and it bothers me. Has anyone ever had this happen to them before or have any idea what the problem could be??? Thanks.

Re: Furnace Odor


I assume you're referring to a forced hot air furnace, rather than a forced hot water.

Perhaps the water in the humidifier got stale with misuse & it needs a changing.

That's my best guess.

Could you advise why the service man was called over?? & have you asked him what he did when he was there.

Perhaps he applied some hi-temp sealant to a crack in one of the ducts, & the odor is wafting via the furnace fan into the living quarters.

Why not call him to see if he can remember exactly what he did when he was there.

I recommend to everyone as a precaution to buy a carbon monoxide detector & keep it in your living quarters---they're only $15-$20 & they are cheap protection against even minute levels of CO that might be transmitted to the living space via a small crack in the furnace heat exchanger.

The CO detector will start chirping even if it detects a small amount of CO, thus allowing you to take action before a dangerous situation occurs.

They're widely available at HD/Lowe's or local hardware stores.

Re: Furnace Odor

Thanks Jack. It was just a yearly routine maintenance check on the furnace (yes, it's forced hot air). I just read over the work performed and the tech cleaned the following: burners, flame sensor, blower motor and skuttle float (which he then replaced). It said he checked for cracks but no mention was made of filling any.

The company did come back to check and found a paper towel in the wheel. He thought that maybe a small piece of it may have gotten pas the wheel to the exchange?? I don't see how that could still be smelling since 2/27/08 when the work was performed?

We did buy a CO detector and that's okay. Also, the water has been changed in the humidifier so I know that's not it. The only thing that was replaced was the skuttle float.

What do they use to clean these things with? Could that be the problem? There was no odor until they came to service the furnace...

Re: Furnace Odor

I'm stumped---could possibly have been some cleaning fluid used---hopefully it will dissapate in a short time.

Maybe some other posters will chime in with more ideas.

Glad to see you have a CO detector----great insurance against lethal combustion byproducts.

Re: Furnace Odor

Often part of a visit includes installation of a new air filter. Since the paper towel issue already, any chance the tech didn't remove all of the plastic film that protected the new air filter, or he installed a contaminated (stinky) one? or possibly backwards (air flow direction)? Or didn't change the filter but contaminated it while cleaning, oiling, checking the fan?

First thing I'd do is swap out the air filter with a fresh new one (or set of filters if applicable) checking the zone and the inlet to the fan (squirrel cage may slide towards you on a glide) with a flashlight before installing new one/s looking for bits of plastic film might be burning up/melting in/on the fan motor or the post. Give the old filter a sniff - it might be the stink source (example lubricating oil or cleaning fluid or contact cleaner used on the fan, or scale remover might have been dripped on or oversprayed on it while in the tech's truck or during his work. Since the company has been back out to look things over (found the towel) assume they saw no problems with the flame adjustments and no burnt wire insulation.

If the blower motor slides out (with the safety switch in the OFF position) take a peek and a sniff - sadly some techs don't use a brush and vacuum or blow out first to remove dry debris accumulations off of the motor housing and fan blades, just douse the whole thing with cleaner - might also be the source of not yet evaporated cleaner or lubrication on a now wetted mud/dust/hair accumulation on the blower motor.

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