Why we have burn bans in cold weather

By Camille St. Onge and Melanie Forster

During chilly days and nights, a warm fire is appealing. However, it’s best to think twice before building a fire in your wood stove or fireplace in case there is a burn ban. What many may not know is that often times the coldest days can be the worst days for burning wood.

Why burning in the winter can be an issue

Normally, the air closest to the ground is warmer than the air higher up.  This allows air pollution like

smoke, vehicle exhaust and dust  to disperse and not reach high levels below in the air we breathe. During the winter, sometimes these conditions are reversed—cold air below and warmer air up high. This is called, not surprisingly, an inversion.

During an inversion, air pollution fine particles become stagnant and don’t move up the air column. They are trapped close to the ground, in the air we breathe. These fine particles travel deep into our respiratory system and lodge in our lungs. This is unhealthy for everyone, but is especially harmful to infants, young children, the elderly, and people with asthma, heart or lung disease.

Forecasting weather, air monitors and burn bans 

There are nine air authority agencies in Washington with forecasters that monitor weather patterns and assess air quality on a daily basis. Forecasters watch weather and air quality models closely to identify areas with weather and pollution patterns that will cause air quality to reach unacceptable levels.

Air monitors placed throughout the state provide valuable data about air pollution. Through air monitoring and weather modeling, forecasters are able to identify communities that will experience air pollution problems during inversions. Once a community is identified for an air pollution problem a burn ban is put in place to help keep air pollution at acceptable levels.

Some areas are more susceptible than others for air pollution buildup because of the geographic makeup of the region. Good examples are Leavenworth and Colville, which are in narrow valleys. Other areas are less obvious bowl-shaped areas like Spokane. Cold, dense air gets trapped in these areas and pollution builds up near the ground.

Because outdoor burning and indoor wood heating contribute significantly to air pollution during inversions, residents and businesses may be required to restrict burning. Washington has two stages of burn bans: Stage 1 is applied when air pollution levels are elevated and are expected to continue to increase to unhealthy levels; Stage 2 is applied when air pollution levels are approaching unhealthy levels and the air cannot accommodate any more pollution without becoming unhealthy.

Stage 1 burn bans

During a Stage 1 ban, all outdoor burning and use of uncertified wood stoves, fireplaces and inserts and other devices is prohibited, unless they are a home’s only adequate source of heat. Prohibited outdoor burning includes residential, agricultural and forest burning. Certified wood stoves, pellet stoves and other certified wood-burning devices are allowed.

Stage 2 burn bans

A Stage 2 ban applies to the use of all certified and uncertified wood stoves, inserts, fireplaces and other wood-burning devices, unless they are a home’s only adequate source of heat. Stage 2 bans also prohibit all outdoor burning.

Washington’s burn ban website and resources

Before lighting a fire, find out if your county has a burn ban in place by visiting www.waburnbans.net.

Ecology has several resources available about indoor burning, including a list of approved wood stoves, fireplace inserts and other devices on the Air Quality pages. You also can find tips for burning properly in a previous blog story: How you burn makes a difference in your pocket and in the air.

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