Is this a fire hazard?

Steamhead (in transit)

or just dirt? If the fiberglass shows no sign of melting, it may just be dirty.



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TraderH

I have an older home with a oil fired steam boiler with cast iron radiators thoughout most of the house. There is a newer section of the house which has hot water baseboard with the water being heated by the steam boiler. While renovating, when we opened the wall housing the hot water baseboard loop to the second floor that the copper pipe was directly in contact with the paper vapor barrier covering of the fibreglass insulation in the wall and the are in contact with the copper line was black and charred in a good 2" band throughout the length of the run. It appeared that it had smoldered and almost ignited at some point. This doesn't seem possible with the temperatures generated by a steam boiler - let alone a hot water loop off of the boiler - but they do travel in a very tightly enclosed insulated space. Do you think what I was seeing was an actual risk of combustion or perhaps a chemical reaction of the facing with the copper piping and all the heat? What should I do at this point when I want to put the wall back together? The hot water loop was not installed properly as it travels along an outside wall and we only have 2x4 studs in the wall cavity.

Thanks for the input.

TraderH

Corrected the typos in the original question

I have an older home with a oil fired steam boiler with cast iron radiators thoughout most of the house. There is a newer section of the house which has hot water baseboard with the water being heated by the steam boiler. While renovating, when we opened the wall housing the hot water baseboard loop to the second floor we saw that the copper pipe was directly in contact with the paper facing of the fibreglass insulation in the wall and that the area in contact with the copper line was black and charred in a good 2" band throughout the length of the run. It appeared that it had smoldered and almost ignited at some point. This doesn't seem possible with the temperatures generated by a steam boiler - let alone a hot water loop off of the boiler - but the pipes travel in a very tightly enclosed insulated space. Do you think what I was seeing was an actual risk of combustion or perhaps a chemical reaction of the facing with the copper piping and all the heat? What should I do at this point when I want to put the wall back together? The hot water loop was not installed properly as it travels along an outside wall and we only have 2x4 studs in the wall cavity.

Thanks for the input.

TraderH

It seemed like charring. It was black and in the shape of the indent the pipe made in the paper. It travelled the whole length of the pipe run. I don't believe the fibreglass was melted. I don't thing that the paper fell apart with a little flexing but I didn't test in detail.

Timco

The copper pipe had to be soldered somehow...I have charred a few tight spaces in my day...it is not the pipe...it was the piper.

Tim

Bob Harper

The fire investigation community is collecting information on fire ignition by steam heating. I know several nationally reknowned investigators have written about ignition from steam pipes at the floor where the wood had been wet. The problem is pyrolysis, which is a slow, long term chemical breakdown of combustibles, which lowers the ignition temp.
Did you take any pics?

Steamhead (in transit)

Seems to me

if this were true, the ignition temp could drop to almost ambient.

Do you have any reports or anything else to corroborate this?

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lee_7

As I study fire science in college, heating a combustible over and over does lower flash point to a certain degree. Not a whole lot, but it does lower flash point.

TraderH

Additional Info

Will try to get a picture - I had to open another wall with similar situation. Not as much charring on the insulation but infact still blackend behind copper piping and paper facing is breaking down. HOWEVER - important info - the hot water for the baseboard is being heated by a steam boiler with a heat exchanger but there is nothing to bring the baseboard water temp down to 180 degree range - it is probably operating at 215 degree steam temp. I think that is a major factor in the charring over the years (50 years since installation). I'm updating the boiler and will make sure that the hot water baseboard is operating at a safer temp.

Thanks for everyone's responses.

Bob Harper

pyrolysis studies

The US Forest Products Assn. conducted long term studies on the effects of pyrolysis with various species. They found that after ~25 yrs. under controlled heat,ventilation, and humidity that most species would spontaneously ignite around 225F. That is the primary data for all stated clearances to combustibles. Now, if the wood is allowed to get moist and support fungal action, this process can be accelerated. Sweaty pipes in cold interstitial spaces would be a concern. However, Dr. John Dehaan, the author of Kirk's Fire Investigation, has found ignition of flooring under radiators at pipe penetrations. While there is no stated clearance around heating pipes, perhaps there should be. The problem is, this would require firestopping per the IRC as you cannot leave those gaps open. I have not heard that this is a rampant problem so don't panic. However, the information is growning because up until recently, nobody figured there was sufficient energy present for ignition. They missed the pyrolysis angle. A piloted ignition requires much more heat flux that pyrolysis or that hot bed of contention-pyrophorric carbon, which supposedly can spontaneously ignite in air at room temps.
If I hear anything, I'll pass it on. I do consulting with O&C investigators.

ed wallace

charring of backer paper

you say the hot water baseboard is being heated by a steam boiler thru a heat exchanger and that the hot water is at 215 degrees then you need an aquastat to only allow 180 degree water into baseboard loop most likely the water temp has dried out the paper giving it a charred look

Steamhead (in transit)

It can't be a rampant problem

or there would be no steam-heated buildings left.

It is certainly possible to exceed 225°F in a hot-water system as well, if it's under enough pressure.

I would think properly applied insulation between the pipe and the wood should solve this problem. Pipes should be insulated anyway, now we have another reason to do so.

"Steamhead"

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Bob Harper

steamed up

The 225F was for 25yrs continuous. Not too many boilers fire 24/7/365x25. What is needed is anecdotal info. from guys like ya'll being shared with the fire investigation community.
Thx

Lyle {pheloa} Carter

Charring

I don't know about the fire hazard. I belive what you are seeing is not char but the asphalt in the vapor barrier coming to the surface because of the high heat.

JimNess

pyrolysis

In an effort to expalin the dangers of pyrolysis to our customers. Can anyone help us find accredited articles or information pertaining to pyrolysis cause by improper installation of boilers and or water heaters that are rated for non combustable flooring being placed on cement blocks or over poured cement above a combustable surface.

 Each year we see 2 or 3 fires caused by pyrolysis through cement pads over wood floors.

Thank you,

 Jim Ness 

croydoncorgi

Err.... What about solar-thermal pipework??

If 225 degrees F can create combustion via pyrolysis, what risks are associated with pipework carrying pressurised glycol for solar systems?  In principle, the surface temperature of the pipe could exceed 300F!!



Of course, they SHOULD be heavily insulated with heat-resistant insulation - but mistakes, especially hidden inside walls, could easily happen!

STEVE PAUL_3

An interesting article

On this subject can be found on the Inspection News web site.

go to: 

 www.inspection news.net

click "please enter here"

search Pyrolysis hot pipes

click the 1st link

Scroll down to Bob Harpers article