Wood Stove Safety

Wood stove safety is a little more complicated than most people realize. Here is some basic information to help you do it right.

  • 061 wood stove safety - chimney sweep
    Chimneys should be checked at regular intervals for excessive creosoting... and cleaned?when necessary?by an expert (or a stove owner who uses the proper tools.
  • 061 wood stove safety - connect to chimney
    Two methods of connecting a chimney connector to a chimney flue where the connector must pass through a combustible partition wall. Instead of the asbestos board shown, sheet metal may be used, or a metal lath and plaster finish may be applied in that area. 
  • 061 wood stove safety - safety clearances
    Diagram show clearance margins for wood stove safety.

  • 061 wood stove safety - chimney sweep
  • 061 wood stove safety - connect to chimney
  • 061 wood stove safety - safety clearances

Thoreau wrote of the stumps which he pulled out from his field at Walden Pond: "They warmed me twice, once while I was splitting them and again when they were on the fire." The following is dedicated to helping folks who heat with wood prevent an inadvertent third warming.

Once upon a time, wood stove safety may actually have been (as so many people claim it still is) a matter of using plain old common sense. But—before you assume that your knowledge of campfires and fireplaces will carry you through the installation and use of one of today's complex airtight heaters—consider the fact that not even the "experts" can agree about just what precautionary steps prudent wood burning should involve.

Much of the controversy centers on the fact that safe stove installation and operation are often either inefficient or inconvenient (or both!). And despite the fact that a compromise between absolute safety and 100% efficiency is often necessary, no one can tell you what margin of safety (at the expense of what degree of efficiency) you should choose. However, once you understand the problems and the alternatives involved in achieving the best compromise, you should be well equipped to make such decisions yourself.

Picking a Stove

Far too few consumers know just how important it is to choose a stove of the right capacity for the area to be heated. After all, wood heaters are anything but inexpensive in these days of energy consciousness, and financial pressures often force many folks to opt for a small unit . . . a decision which can lead to overfiring.

And, since the generally recognized safety standards for wood stove installation are based upon normal operaing temperatures (with comfortable margins for error), it's possible for an overheated firebox to ignite walls or other flammable materials which are beyond the "safe" perimeter. (Did you know, for example, that sustained temperatures of slightly over 200°F can actually cause wood to combust spontaneously?)

On the other hand, some shoppers buy top-of-the-line models . . . assuming that a large stove will provide them with heat in reserve. Unfortunately, although the dangers of an underfired heater are less obvious than those of an overfired one, they are equally serious.

Since most owners of large stoves will often reduce the output of their heaters by restricting the air supply with a damper—a technique that reduces burn efficiency, makes more smoke, and forms creosote rapidly—buying a stove that's too large for your needs can be the indirect cause of chimney fires. In fact, such accidents have been known to happen within the first week after the installation of a new stove and chimney.

Because of the chance of such fires, it's imperative that any supposedly airtight stove which is "throttled" (to extend its burning time) actually be sound and well-sealed. Your best defense against a raging chimney blaze is to close up the stove and thus shut off the smokestack's oxygen supply.

However, if your stove has any leaks around its door(s) or damper—or through the body of the stove itself—you can create a disastrous situation by attempting to starve a chimney fire.

You see, if there's a small flow of oxygen to the smoldering creosote, the O2 will accumulate until enough is present to allow the chimney's coating to flash. That ignition will quickly consume all the available air, and the fire will expire again until the oxygen reaccumulates. Repeated flashing—which can happen as often as several times per second—has been known to break apart stovepipe and even masonry chimneys!

All new stoves approved by the Underwriters Laboratories (UL) meet standards of soundness and engineering, but secondhand units often suffer from deterioration . . . so check any used heater carefully! (You can find a number of good hints for selecting an older stove in Barry Dordahl's article "Wood-Burner Restoration" in MOTHER EARTH NEWS) Plus, be sure that the stove you're buying is designed to burn wood: Few coal stoves can accept logs, and no wood stove can safely burn coal without the appropriate grate.

11/30/2007 2:18:27 PM

We just bought an old cook wood stove. We noticed in the firebox an asbestos lining. Could this be why I can't get the oven above 200 degrees. what would happen if we remove it?

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