Burning questions about old wood and baseboard heaters

Q: Over beers, my buddy was telling me that wood in older homes burns easier than newer wood. He said something about the ignition temperature being lower after years of exposure to heat. He says this makes the wood more vulnerable to combustion, almost like a spontaneous combustion kind of thing, making older houses more vulnerable to fires. Can this be?

A: Beer or no beer, your friend is in esoteric territory. He is likely referring to pyrolization - changes caused by exposure to heat, in this case in wood. Those in the fire investigation, chemistry and physics fields have been trying to sort this out definitively for a long time (probably over beers, which is why they still are somewhat baffled).

Wood is pyrolyzed by being exposed to a heat source exceeding 212 degrees Fahrenheit. If the wood is in an oxygen-deficient environment, the surface can become charred. And if that lack of oxygen is followed by an infusion of oxygen, combustion can happen, according to those who study these things.

Does this mean that an older home is going to burn more easily than a newer home? Perhaps, but probably not because of pyrolization. That burn is more likely caused by older wiring, lack of firewalls and firestops, a dirty or unsafe chimney, a lack of smoke detectors, sprinklers or other features that play a much larger role in keeping you safe from fire.

Q: Is it true that you can seal the perimeter of an electric baseboard heater to the wall with caulking, eliminating that black smudging on the walls and ceilings? I have heard that the rising heat attracts the dust inside the wall, burns it and deposits it on the wall. Also, can I paint the exterior of my baseboard heater and, if so, what kind of paint?

A: We tackled the problem of black smudging about two years ago in this space and are still recovering from the crush of mail and homespun theories. The black smudge questions ran the gamut from dirty refrigerator coils to candle burning to carpet pad to mold.

All those theories may have merit, but what seems to be the most prevalent cause is blackening walls above baseboard heaters is an electrical fault in the device itself.

An electronic air cleaner works by inducing an electrical charge on dust then traps that dust on an oppositely charged plate. A complete circuit inside an electric heater normally runs in opposing directions, the AC charges canceling each other out. If a fault is induced, the charged (and crispy) dust particles tend to cling to the walls.

In my own observations I have seen more of this smudging on walls with recalled Cadet heaters and older baseboard heaters, lending a bit more credence to the theory of electrical faults.

The idea of sealing the perimeter of the heater probably got its start from electric wall-mounted forced air heaters that are physically mounted inside a wall, as opposed to baseboard heaters which are mounted on the wall. Sealing the perimeter of your baseboard heater will do nothing, as it has a closed-wall section on the back.

Good housekeeping of the home and heater can help but won't be the total answer. Dirty air can be sucked through a multitude of areas in the home, the hole in the wall for the forced-air heater being only one of many.

As for painting, manufacturers frown on painting most baseboard heaters, but it is done routinely. The outside of the outer casing is the only part that should ever be painted. Do not paint the heating fins!

Use a paint made for high-temperature surfaces like that used for fireplaces or engines. Baseboard heaters are cheap. Rather than paint an old one that's making the walls black, pull a fifty out of your pocket and buy a new one.

Q: I'm repainting my home this summer and want to cover the rusty nail heads that have bled through the old paint. What's the best way to do this?

A: Sand the rust off the nail heads, countersink them all into the siding, caulk over the top with acrylic or siliconized acrylic caulking, spot prime the area around the nail head, and paint the wall.

Postscript:

Some of you had trouble getting to the LP siding-claim Web site included in last week's column. The site address was correct,

www.lpsidingclaims.com

but because the address went onto a second line, there was a confusing hyphen at the end of the first line.

Ask The Expert answers readers' questions every Saturday. Send questions to Ask The Expert, Seattle Times, P.O. Box 70, Seattle, WA 98111, or call 206-464-8514 to leave your questions on Ask The Expert's recorded line. E-mail address is dhay@seattletimes.com

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