CHIMNEY FIRES

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Creosote-reducing devices. In MOTHER Nos. 73 and 74, Jay Shelton and Claudia Lewis reported on their tests of several stove attachments that were designed to reduce the rate of creosote accumulation in chimneys. The most effective of these were catalytic converters and barometric draft controls. A properly designed and operated catalyst can cut creosote deposits by more than 90%. A catalyst is most effective when integrated with the stove's design. A barometric draft control dilutes the smoke, allowing it to pass out of the chimney without leaving creosote behind. Shelton and Lewis found that the device can reduce creosote accumulation by up to 75% but noted two liabilities: It allows warm house air to escape up the chimney and will provide a chimney fire with air.

Chimney Cleaning

How often should you clean your chimney? About the most advice anyone can offer is to do so whenever deposits reach 1/4" in thickness. This may happen in a matter of days in a poorly designed chimney connected to a woodstove operated at very low output. Or it may take years in a well-designed system attached to a good catalytic stove. Check your chimney weekly until you learn how its installation and your operating techniques affect creosote.

SAFE STOVE INSTALLATION

A>CAP AND SPARK SCREEN
B>>FLEXIBLE ATTACHMENT TO PREVENT STRESS-CRACKING.
C>CHIMNEY TOP AT LEAST 3' ABOVE ROOF PEAK
D>ROOFING AND RAFTERS HELD BACK AT LEAST 2" FROM THE CHIMNEY
E> AS MUCH OF CHIMNEY AS POSSIBLE INSIDE THE HOUSE
F>JOISTS HELD BACK 2" FROM CHIMNEY
G> CONNECTOR PENETRATES THIMBLE AT LEAST 3"
H>ALL JOINTS FIXED WITH SCREWS
I> TILE THIMBLE
J> AIR SPACE
K> TILE LINERAPPROVED CATALYTIC WOODSTOVE IS PREFERABLE
L> CLEAN OUT

What to Do When It Happens

When a chimney fire finally does get started — and for most wood burners, it's a matter of when, not if — it will announce itself dramatically. The normal crackle will be overwhelmed by a roar often likened to a 747 taking off up your chimney. You'll hear air being sucked through the draft control, and stovepipe sections may even shake. The connector may begin to glow cherry red.

Chimney fires most often occur when starting a fire, when refueling, or during an unusually hot blaze. Flames, allowed to burn intensely to ignite new fuel, lick into the chimney and, if there's enough oxygen, ignite the creosote. Heat in the chimney drastically increases draft, inducing the flames to rise through the entire system. One thing leads to another, and in short order you've got a raging inferno that can destroy the chimney and even burn down your house.

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