# Burning smell from heated painted PEX?



## kmwest (Dec 10, 2016)

Our natural gas boiler is about 30-40 years old (manufactured 1987, first service sticker was 1994, so I assume about 35 years old).  It's in our unfinished basement.  A few months ago we had the entire basement (walls, floors, ceilings, exposed piping) painted and there is still a mild paint smell.

Since we started using the boiler this winter there is a light campfire smoky smell that starts going through the basement after the boiler's been running for 10-15 minutes.  All the burner flames are blue and I just drained the expansion tank this morning due to it not maintaining water pressure and losing water from the TPR valve.  We have a combination smoke/CO detector on the other side of the basement and it hasn't gone off.

This didn't happen last winter at all.

I might be imagining things but it seems to be most prevalent in the areas right under the hot water piping - both the PEX from the boiler and the hot water lines into our bathrooms and kitchen.  I don't get as much of a smell from the boiler itself.  Could this be from paint on the pipes, or the joists that they're on, heating up and creating fumes?

FWIW this smell dissipates when the boiler's been off.  We turned the heat off overnight so I wouldn't scald myself in the expansion tank drain this morning, and there was no smoke smell.  After I completed the drain, refill, and started the boiler again the smell started about 15 minutes later.

Thanks for any advice.  I'm obviously concerned but don't want to worry unnecessarily.


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## Snoonyb (Dec 10, 2016)

Was the paint oil or water based?


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## kmwest (Dec 10, 2016)

The floor paint was acrylic and latex... don't know about the ceiling paint that would cover the pipes, or about the primer.


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## Snoonyb (Dec 10, 2016)

Thanks.

You'll experience more out-gassing from oil based.

Is there any apparent discoloration above the appliance or on the pex near the source?


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## kmwest (Dec 10, 2016)

Snoonyb said:


> Thanks.
> 
> You'll experience more out-gassing from oil based.
> 
> Is there any apparent discoloration above the appliance or on the pex near the source?



None that I can tell.  I can post photos but nothing looks discolored - but it is black paint on the ceiling.  What do you think may be an issue?

I just went back into the basement and the boiler is cold now that the house is back up to programmed temperature. No smell in the same place that had it the worst earlier.

Edit: my arithmetic is bad, the boiler is about 25-30 years old since it was made in 1987.


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## Snoonyb (Dec 10, 2016)

Any discoloring will probably began to appear as toward the brown area of the spectrum.

I would monitor it for a week, for a gradual dissipation of the odor, which should occur as  the "baking-in" of the paint continues.


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## kmwest (Dec 10, 2016)

Snoonyb said:


> Any discoloring will probably began to appear as toward the brown area of the spectrum.
> 
> I would monitor it for a week, for a gradual dissipation of the odor, which should occur as  the "baking-in" of the paint continues.



So any discoloration would just be due to the heat onto the paint?  Or another issue?


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## Snoonyb (Dec 10, 2016)

Yes, if it occurs at all, it will be over time and if the paint was a flat you may, over time, notice a shading effect.


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## slownsteady (Dec 10, 2016)

Could also just be burning off accumulated dust after sitting idle for the summer. Is this the first time you're using heat this winter (fall)? AS Snoonyb said, watch things and see if the smell dissipates over time.


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## Snoonyb (Dec 11, 2016)

Yep! In retrospect and it's because I automatically do a routine cleaning at the start of every heating season, another issue would be, had a general cleaning been accomplished prior to firing up the appliance.


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