In rural northern Wisconsin, it’s too soon to put away snow shovels and too sloppy to wash road salt off vehicles. Folks here celebrate any hint of spring by comparing how much sap they gathered, how much maple syrup it made, and how many tomato and pepper seedlings they’ve started indoors. But overnight temperatures are likely to drop into the 30s or lower for a few more weeks. So our home heating season is far from over.
In Wisconsin, about 1 in 33 households heat with wood. Up North, where forest products are a major industry, I know relatively few people who don’t use wood as a primary or secondary heat source. So in these parts, spring is also known as chimney fire season.
Why spring? There are several reasons. After a long, cold winter some families may be running low on seasoned firewood. Wood with a higher moisture content produces smoke that’s cooler and more likely to condense in the chimney, leaving combustible deposits.
But even well-seasoned firewood releases smoke, water vapor, gases, unburned wood particles, and other substances that condense and stick to the inner walls of the chimney. It’s called creosote. In spring, rising outside temperatures mean we don’t need to produce as much heat indoors as when it’s colder. Adjusting dampers to restrict the air supply to the fire to regulate heat can hold the smoke in the flue longer, allowing creosote to build up faster than a fire given a less restricted air supply. Conventional wisdom says a chimney fire is most likely to occur when you’re burning very hot fire. Very often, that comes after a warm spell where a cooler fire allowed creosote to build up. It can take as little as a ⅛-inch build-up to ignite and become a chimney fire. So when a cold snap comes after a warm spell, your volunteer fire department isn’t surprised by chimney fire calls.
Even well-seasoned wood-burning homeowners have chimney fires. Shortly after my husband joined our volunteer department, he had to call for help with a chimney fire at his own house. He was letting the fire die down to clean the chimney when a spark ignited the creosote. Soon there was thick black smoke rolling out the chimney. That was in the late 1980s when this department used a telephone tree to call members to respond to a fire (yes, before radios and pagers – even before 911). The guys showed up, got the fire out, and cleaned the chimney. And after they left he fired up the stove again.
That chimney ran from the wood stove in the cellar of our old farmhouse up through the main floor and the unheated second-story bedrooms (which often was colder than winter camping). The stove kept one downstairs interior room at a comfortable temperature and three downstairs rooms above freezing. On really cold days you could see frost on the paneling nails in our bedroom. There wasn’t much insulation in the place. The fieldstone foundations, built every time there was an addition, made it just about impossible to upgrade the ancient ductwork for the vintage propane forced-air furnace that was our back-up heat source. So we burned wood – about 20 full cords each year. A full cord is a stack that’s 8 feet long by 4 feet wide by 4 feet high – 128 cubic feet.
Shortly after we were married, that chimney deteriorated to the point where we needed to replace it (which we couldn’t afford) or stop using it. So we stopped using it and made the back-up woodburner in the first-floor kitchen our primary heat source. The kitchen chimney was shorter and we were able to barter with a mason friend, who rebuilt it in exchange for a canoe. We had a fire in that chimney, too. And there had been at least one before Bill bought the house: You could tell from the charred boards around the chimney in the attic.
Bill isn’t the only firefighter in our department who has had to call for help with a chimney fire. At one guy’s house, they found a wasp nest between the metal flue and the attic trusses. It may take a long time for the flammable material in a critter nest to actually ignite. But it can – no matter how clean you keep the inside of your chimney. And if it does, it can quickly become a structure fire.
One thing you never want to do with a structure fire is give it oxygen. Nevertheless, it’s common when you burn wood to have an occasional backdraft puff smoke out into the house. To clear the smoke, what do we do? We open windows. And that’s exactly the wrong thing to do if it’s not just backdrafted smoke from a fire safely contained within a firebox, stove pipe and flue.
If a chimney fire has ignited other combustible materials, opening windows will feed the flames to produce more heat and more flames. In some rural areas it may be 10 or 15 minutes or longer from the time you dial 911 until volunteers and equipment begin to arrive. Even then, it takes a few minutes to set up a water supply, position hoses, and start an exterior attack. Most fire departments won’t do an entry or begin an interior attack unless or until water is available and there are sufficient personnel on scene to work in teams, backed up by other teams prepared to get the first team out if things go south. Like many rural departments, we have mutual aid partners we call in to supplement our own resources, including personnel. But it can take 30 minutes – or more – for them to arrive.
In the meantime, fire may be growing and spreading. It’s hard for homeowners to stand by and just watch while that happens. It’s also hard for firefighters to see their neighbors make a last-second attempt to rescue pets, knowing that opening a door can give a contained fire enough oxygen to engulf the structure.
Not all chimney fires roar loud enough to be heard inside, shoot sparks into the sky, or do anything else obvious enough for rural neighbors to notice. So you may not be sure you are, in fact, having a chimney fire. In that case, it’s best to err on the side of caution: Grab your cell phone and get family members and pets out of the house, closing doors behind you. Call 911 and be prepared to wait at a safe distance until they’ve inspected the building and it’s safe to go back inside.
|If You Burn Wood…|
Here are some precautions you’ll want to take.
1. Study resources like woodheat.org .
2. Regularly clean chimney and stove pipes and inspect in and around the heat zone.
3. Keep a Chimfex Chimney Fire Extinguisher readily available and regularly review how to use it (this video is helpful).
4. Keep fire extinguishers near the chimney on every level of the home.
5. Keep a ladder accessible for quick access to the roof.
6. Keep working smoke detectors on every level, test them monthly, and replace them every 10 years.
7. Do regular family fire drills so everyone knows two ways out of every room and where to gather outside the structure.
8. Check with your homeowners’ insurance to be sure your wood heat system is covered.
Spring isn’t the only season for chimney fires. We’ve had memorable calls in fall and winter, too. One house’s chimney was as tall as the one in our old farmhouse. The contingency plan there, if the fire spread, was to call in an aerial unit that could drop water from the extended ladder. At another call, the weight and chain we often drop to break through a blockage glowed cherry red when pulled out of the chimney. At one smoke-filled cottage, we had to break down a door for entry while neighbors tried to reach the owners, who were riding trails in the next county over. One two-story home had a metal roof so slippery we discussed calling an ambulance for stand-by (imagine the comments about that: “Seriously, stand-by for a chimney fire?!“). One Christmas Eve the guys made extra-sure the fire was not only out but the chimney was safe for Santa.
At one, we thanked God the homeowner let her kids sleep downstairs that night instead of sending them to upstairs bedrooms. Everyone got out safely. At another, the homeowner climbed his antenna mast to get on the roof to fight the spreading fire with a garden hose. An officer talked him down shortly before that section of roof collapsed.
Recently, the first page we got identified the situation as a chimney fire but was almost immediately amended to “chimney and roof.” Our chief immediately called in mutual aid so five departments from two counties responded. After several hours on that scene and a couple more washing and repacking hoses, filling tanks, and checking fittings, here’s what two of our volunteers did.
One went home to a cold house. She had been letting her fire go out so she could clean the crossover that connects the riser from the firebox to the chimney.
Another had plans to install a new wood pellet stove – one of few affordable models acceptable to his homeowners’ insurance company. His family had been using space heaters to get by for a few days after their furnace died.
Bill and I came home and turned up the thermostat. After all those years of burning wood in the old farmhouse and having bronchitis more times than I can count, when we built our new house we opted for radiant hydronic heat. We lived in the house for a year before installing that system, and heated 1,120 square feet of blessedly insulated space with a small wood stove. Now we only burn wood in fall and spring when a small morning fire is enough to take off the chill and a small evening fire just feels good. And when spring ice storms knock out our power, like they have twice recently.
That’s spring in northern Wisconsin.
Donna Kallner writes from rural northern Wisconsin, where she is a member of the Wolf River Volunteer Fire Department.