I probably should have asked this before doing it, but I will now anyways.

I have noticed mice coming in and out of the (fairly large) hole where the baseboard heater pipes are. I removed the casing and added a bunch of steel wool to it + spray foam. I am now concerned if this is a fire hazard - having all of this dry foam near a heater?

I attached photos of what the area looked like before / after.


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  • Hello, and welcome to Home Improvement. Good question; keep 'em coming. And, you should probably take our tour so you'll know how best to participate here. Sep 18, 2019 at 11:35

2 Answers 2


Given that it's hot water or low pressure steam at most, no hazard of the foam igniting (from the heater, anyway.)

Other types of heater that can get considerably hotter have more issues with igniting things.

  • 1
    There may be some additional out-gassing of the foam due to the extra heat however. Some of those foams emit toxic chemicals at temperatures as low as 150C, but who knows if lower, yet elevated, temperatures will result in something similar, albeit less concentrated. polyurethane.americanchemistry.com/…
    – JRaef
    Sep 17, 2019 at 22:16
  • 1
    150C is 30C higher than residential steam systems in any sane part of the world. Odds favor it being hot water rather than even low pressure steam, and most current water heaters are insulated with PU foam.
    – Ecnerwal
    Sep 18, 2019 at 0:23
  • Thanks for the help Ecnerwal - I guess I'm mostly concerned that the temp of the pipe itself may get hot and cause an issue with the foam since I sprayed the foam into the hole, and its around the pipe. Thanks again!
    – James
    Sep 23, 2019 at 22:49

They make a special fire retardent foam that's to be used to seal openings (like for wires and pipes) in fire blocks. It's pink in color. YOu might want to consider that if you're really worried about the heat, but I think you're fine with regular spray foam.

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