View Full Version : Gas heater smell

02-05-2011, 01:35 PM
Guys, I have a small issue that's driving me nuts.

I have a non-vented "blue flame" heater running on natural gas. Similar to this:

It does have a fan pushing the hot air.

I use it to keep a small building at roughly 50F in the winter. It ran fine last winter. This winter it still runs fine but now has a noticeable smell. The smell is somewhat similar to the kerosene smell you get from torpedo jobsite heaters, only not as strong. I say similar, because it's not quite a kerosene smell, don't know what else to compare it to.

There is no CO given out and the flame is all normal blue with an occasional orange spike here and there. I've taken it apart and couldn't find any parts overheating/melting/etc.

Any idea what this may be and /or how to troubleshoot?

James Eggert
02-05-2011, 02:00 PM
The only time I have odor issues with my kerosene blower/torpedo is when there is water in the fuel.

You say natural gas; is it possible they changed either the type or amount of the rotten egg smell additive? Probably worth a call to ask, although you may not get a truthful answer!

johnny watt
02-05-2011, 02:13 PM
Sometimes when people complain of odor, and it is not caused from a gas leak or venting problem, the cause is from a chemical in the home such as recent painting, or minor gasoline fumes from when they store the weed whacker in the basement for the season. That creates a much stronger and different odor when it is being burned as part of the combustion air.

Does it have a replaceable catalytic part?
How about just a good cleaning for dust?

02-05-2011, 02:46 PM
Jim, no it's not the additive, my house is connected to the same supply and no smell from the kitchen stove.

Johnny, there is no gasoline, paint or any other fumes in the building. It is not a catalytic heater, just a normal burner. Yes I did clean the dust off the burner, made no difference.

The burner is a stainless (horizontal) cylinder the width of the whole unit, with tiny holes for the gas on top, look like laser cut slots.

02-05-2011, 03:05 PM
You might want to check to see how the pilot and/or venturi tubes are adjusted. They may have some dust/crud built up on them. I have seen this be the source of strange smells on other natural gas furnaces. In my experience if the tubes are not adjusted just right the gas does not burn cleanly and you can have that rotten egg smell. You mentioned that you occasionally see a yellow spot in the normally blue flame. I'm thinking the venturi is your culprit. Of course, YMMV...


02-05-2011, 04:38 PM
Thanks Don. There are no adjustments. The venturi is the inside of the burner and is clean. I did take out the metering orifice that dispenses the gas into the venturi and it is clean as a whistle.

As a test, I turned on the kitchen stove on max and inhaled the exhaust for a while. It's the same smell, only much less in the kitchen. So apparently it's the same exhaust products, only much stronger in the heater. The BTUs are comparable (around 25k), so they should smell about the same.

The heater actually burns with a cleaner blue flame than the kitchen stove so I'm stumped.

Chuck Kiser
02-05-2011, 05:06 PM
I turned on the kitchen stove on max and inhaled the exhaust for a while. So I'm stumped.

To good to resist, I HAD to misquote you. :>)

David Meiland
02-05-2011, 05:06 PM
There is no CO given out

What did you check it with?

02-05-2011, 05:30 PM
David, I have a CO detector 10 ft away from that heater. It has a digital display that reads in ppm. Currently reading zero. Can't say how accurate it is, but I did check it a while ago and it was fine. I think it measures 10ppm and up.

CO is also an indication of incomplete (rich) combustion and I don't see that in the flame.

02-05-2011, 05:41 PM
I turned on the kitchen stove on max and inhaled the exhaust for a while.

No thanks, I'll take a beer or margarita. Or both.

David Meiland
02-05-2011, 06:44 PM
a CO detector

If it's a UL-2034 unit it may not be very good, especially at low levels. It probably would show something if you had a major problem. The better units are well over a hundred bucks, and they need to be up where you would install a smoke detector. I would expect 10-20 PPM in the undiluted flue gas of a typical water heater, definitely not zero, and at least a few PPM from a really good cooktop burner flame with nothing on the burner.

The rule of thumb for propane is that 5 gallons burned yields a gallon of water vapor... a significant source of humidity. NG is probably similar. Flue gas has a wet smell that I can detect easily even in small quantities. I did a blower door test last month and pulled flue gas out of a direct vent fireplace that had a factory defect. Only the pilot light was burning, no burner flame, and the house was really drafty, but I could smell it anyway.

And of course you could be smelling methyl mercaptan used to scent the fuel.

I would check it out with a combustion analyzer a foot or two in front of the unit, and check the gas line and the unit itself with a gas sniffer. If nothing is found, forget it.

02-05-2011, 07:22 PM
David, I think you missed my purpose. I'm not worried about CO, I spent many hours in there already with no ill effects whatsoever. It's the smell that annoys me and there was no smell last winter (installed the unit at the beginning of last winter).

No it's not methyl mercaptan. I know that smell.

David Meiland
02-05-2011, 08:52 PM
I understand that you want to know what the smell is. My guess is that it's the water vapor in the air, and that the exact makeup of the NG you are getting has changed. When I lived in CA (and MI) we had NG. One day on a remodel my plumber was moaning about how the utility company was now buying gas from Texas... the water in it had some objectionable quality or other... it was a new problem. Maybe if you got the right MichCon person on the phone you would be able to get some inside dope on exactly what they're selling this year.

02-06-2011, 01:46 PM
David, I burn the same gas in the kitchen and I get almost no smell at all from a comparable size (btu) burner. So it's not the gas.

James Eggert
02-06-2011, 03:48 PM
OK, same size burner(+/-), same blue flame(visual), no smell in kitchen when you sit next to the flame, what's left?

It burned ok last year, you cleaned it this year, but, if there is a small teensy odor, there has to be one of the ports in the burner not igniting, whether you cleaned it or not! There are only two options for these generally clean burning units.....one is it's out of adjustments in some way or one or more of the burner ports are not igniting. This could be a pressure thing thats is different than last year.

Any chance you added another gas burning appliance, and sometimes when it is on, it lowers the available gas to the heater??

02-06-2011, 07:19 PM
No, there is no new appliance, but funny you mention gas pressure. When I first bought the heater, it didn't work right and the manufacturer insisted I had gas problems. So I actually tested at that location for pressure and flow. Eventually they replaced it and the new one worked fine.

I will do another check but I doubt I would get a nice blue flame with insufficient pressure/flow.

Yes, I'm running out of suspects, that's why I posted here :)

02-06-2011, 07:28 PM
Check fan and double check environmental's.

02-08-2011, 07:44 PM
You cannot rely on a off the shelf CO alarm for testing appliances for CO. As Dave M. was saying, the UL 2034 std. has deliberately dummied these alarms down so they don't alert at less than 69ppm for less than 30 days and 70ppm for 4hrs. A GRI test demonstrated all the alarms tested were extremely unreliable and inaccurate. The only thing to trust is a professional combustion analyzer that is calibrated and zeroed. You cannot gauge CO production by flame color. What you are smelling could be aldehydes--paraladehyde or acetaldehyde. If so, then there has to be CO present. I recommend you get a professional inspect and test this unit who is certified by the National Comfort Institute as a Carbon Monoxide and Combustion Analyst.

As for your lack of ill healt effects perceived, understand symptoms are a late sign of CO poisoning. You can be suffering from chronic low level CO poisoning with no outward signs or symptoms.

Don't mess around ---get it checked by a pro with professional instruments.

johnny watt
02-08-2011, 09:52 PM
Not to discourage anyone from getting a professional reading, but when the nighthawks first came out with the digital readouts about 16 years ago, I responded to three or four CO calls and the readouts lined up right on the money with the calibrated Gas-Sentry professional carbon monoxide detector used by our utility. Even down at 4-5 ppm.

02-09-2011, 02:38 AM

The digital readout CO detectors I have in that building and also in the house were checked against pro units in the past and they lined up pretty much right on the dot.

We're not talking about level of accuracy here. The units (two different units) read ZERO.

But since I'm grasping at straws, I will check them again next time I see my HVAC guy.

Heartman, you are correct that they don't "alarm" until certain levels. They DO however detect and correctly display down to below 10ppm.

02-10-2011, 07:55 AM
I have used the Empire heater you refered to for about four years. Using propane not gas but also maintaining 50 degrees. When I get a fuel smell I will crank up the t-stat to the max setting and let it run for 20 to 30 min. It seems to clear it out and the flame runs cleaner. This was also suggested to me by the installer.


02-10-2011, 03:01 PM
The plot thickens.

I had the gas company send a crew for a look-see. They came with sniffers. Confirmed smell. Measured zero CO, zero combustible/explosive gases. Claimed their sniffers would show the presence of common toxic gases. No indication of that either. They had not seen this condition before, but confirmed the smell was vaguely kerosene-like.

After some phone conversation with their supervisor, the supervisor offered the opinion that it may be caused by combustion of vapors in the air from some type of petroleum-based product. Problem is, no petroleum products in the building. At any time.

Anybody have a gas chromatograph I can borrow?

02-10-2011, 03:15 PM
I have two, both avail for sm rental fee + delivery and tax.

Reactive chem forensics will be fun for you though. Have you eliminated building on superfund site and/or hydraulic fracking in the area yet?

02-10-2011, 03:28 PM
fracking in the area yet?

Absolutely not. This is a respectable and conservative neighborhood.

David Meiland
02-10-2011, 03:41 PM
Anybody have a gas chromatograph I can borrow?

Not exactly, but there are plenty of ways to send in air samples for testing.

02-10-2011, 04:09 PM
May be simpler to just spend a few days and nights out there sniffing the good life and then send in hair samples. Being a good conservative neighborhood it's not like anything else would show up in that test....

Little has been said of other environmental possibilities like open shoe polish, freshly cleaned and oiled Uzi collection, dust from foam backed carpet degradation, any number of water based, cooking, laundry, cleaning, gluing [epoxy grout...] products that do contain arene's or similar. It's obvious that neighborhood is chock full of free radicals.

02-10-2011, 05:14 PM
Actually I did say about environmental. Nothing changed in that space anywhere near the time period when the smell arose. No chemicals or cleaners were ever kept there except maybe a bottle of 409 or such, and nothing CHANGED. I don't clean the Uzis there, they're in the bunker with the Tommys and the hydraulic frackers.

The gas co. did have a sensible idea. Set the tstat on a high temp so it runs continuously for a couple of days (normally I only run it very infrequently). If there was a temporary vapor in there, it would all get burned out and be done. Then air it out. If the smell persists after that, there is still something getting in there somehow. Or it's not the air.

They did confirm that my kitchen stove gives a similar smell, only much, much weaker, almost imperceptible. They didn't have a theory for that.

And I did ask about any changes in the gas mix at the utility. No changes.

I love puzzles.

02-10-2011, 07:58 PM
Something changed lest you knot be here pondering, no? Since they detected in both locations indications would point to gas supply, atmo inclusion [is there a refinery in the next door neighborhood?], or most likely and common to both structures is you. I know it's not April yet, but try a shower and cut out the pickled asparagus and see it that clears the air.

02-12-2011, 05:57 PM

I ran the heater continuously for a couple of days. Then aired out. The smell is gone.

Seems to confirm the theory that there was something in the air (odorless) that produced a smell when combusted. Appears I have "burned off" all of it by running the heater. Don't know what it was, or how it got there, but appears gone now. For the moment.

Would make a good "Twilight Zone" episode.

02-12-2011, 06:02 PM
Would make a good "Twilight Zone" episode.

Yeah. Scary.

johnny watt
02-13-2011, 12:42 PM
One time while investigating a similar complaint, when the culprit could not be traced to recent painting, hardwood floor finishing, small gas engine storage, manicures or pedicures, moth's balls, etcetera, it turned out the floor drain in the basement was not adequately isolated from the body shop a few doors down.