A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Why is it dangerous to burn wrapping paper?

December 8, 2006

Dear Cecil:

A fire department official appeared on our local news tonight, giving holiday-related fire prevention tips. One was: don't burn discarded wrapping paper in your wood-burning stove or fireplace. When asked by the interviewer why this was a bad idea, the official stated that the paper burned at a higher temperature than most stoves or fireplaces were rated for. I find it hard to believe that wrapping paper could achieve a higher burning temp than, say, a good piece of oak or maple. I suspect that if there's any drawback to this practice at all, it would be the excessive amount of ash produced and/or the ink or other coatings producing possibly toxic gases or chimney-clogging by-products. What say you, Cecil?

Cecil replies:

Be kind. It's tough enough getting local functionaries straight on the basic message — you're expecting miracles if you want them to grasp all the fine points. Burning wrapping paper in your stove or fireplace is a bad idea, but not because you're going to exceed some mysterious rating. Rather it's because, among other things, you don't want to set fire to your roof.

What's called the adiabatic flame temperature (the theoretical maximum) is roughly the same for wood, paper, and many other organic substances including propane, believe it or not: about 2000 degrees Celsius. The actual flame temperature is less, often a lot less, and varies widely depending on how readily the fuel can be supplied with oxygen and how well it burns — meaning, for our purposes, how wet it is.

Moisture content is one big difference between wood and paper. Air-dried oak firewood contains about 20 percent moisture, which must be boiled off during burning. That takes energy, which slows combustion of the wood. Dry paper may contain less than 5 percent moisture and so burns more quickly.

The second and more important reason paper can burn hotter in a fireplace has to do with how quickly oxygen can combine with the fuel. Toss a wad of paper onto a pile of burning logs and what happens? It flares up, sending a wave of heat out into the room and up the chimney. Sure, the logs are more massive and contain more potential heat energy. But the paper has a much higher ratio of surface to mass, enabling oxygen to get to the fuel faster. Whatever potential heat the paper contains is pumped out more quickly and at a higher temperature.

That's one problem. A related one is flame height, especially if you pile the paper high. Over time the inside of a chimney often accumulates a coating of creosote, resin, and other partially burned but still combustible gunk. If the flame height and temperature is such that this stuff overheats, you've got the makings of a cozy little one-alarm fire.

Let's not forget embers. When you burn paper in the fireplace, flaming bits often break off and shoot up the chimney on the updraft from the paper-stoked blaze below. Assuming these make it out without igniting the chimney itself, they might land in a snowdrift if you're lucky or on flammable roofing if you're not.

Finally, as you suggest, there are all those cheery images printed on wrapping paper. No question, from a graphic design standpoint, today's gift wrap is a million percent better than it was when I was a kid. But the fumes from burning ink are just as toxic as ever.

So cut the fire marshal some slack — maybe he was a little vague on the details, but he had the right idea. Discarded wrapping paper should be saved for reuse or put out with the trash, not consigned to the flames.

The fire is the wrong place for other holiday detritus as well — der Tannenbaum, for example. My assistant Una had an Uncle Bob, a manly man who felt throwing the Christmas tree away was a waste of good firewood. So he tossed it in the fireplace — gave him a nice warm glow. Unfortunately what was glowing was the roof, presumably ignited by embers. Fortunately the fire was small and anybody with a hose could have put it out. Unfortunately the hose was frozen solid and the fire department had trouble getting the nearest hydrant to work. Fortunately the firefighters were able to throw a ladder up against the house and put out the fire with a chemical extinguisher. They then hacked off a small hunk of charred roof with axes, peered into the crawl space, and declared the fire out. Unfortunately, having by now found an operational hydrant, the firemen declared they needed to hose down the roof "as policy," sending a torrent of water through the hole and collapsing the living room ceiling. Really unfortunately, the house that all this happened in belonged not to Uncle Bob but his in-laws. Bob bought them an RV and matters were pronounced square, but it was a lesson he won't soon forget, and neither should you.

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