Clearing the Air: Wood Stoves are Killers

Clearing the Air: Wood Stoves are Killers
Image by Tom Frantz

By Tom Frantz

Guess what is dirtier than an old diesel truck hauling dead cows to a rendering plant in West Fresno? The answer is a wood stove. According to a Danish paper on the dangers of wood burning in residential areas, a wood stove puts about 50 times more particulates into the air than a pre-2010 diesel truck per unit of energy produced. And those numbers are from supposedly clean, EPA certified, wood stoves.

The California Air Resources Board (CARB) did the right thing several years ago when they said all new diesel trucks must have particulate filters. Fine particulate matter (PM2.5) is a killer. It is the number one type of pollution shortening lives and causing lost work days in the San Joaquin Valley. It affects everyone including the unborn. Children playing outdoors in polluted air will likely have a debilitating cardiovascular disease at retirement age. Brains damaged in the womb through a mother’s exposure to fine particulates leads to lower IQ’s and all sorts of maladies.

While CARB is doing their part with mobile sources, our air district has failed to make a plan for sources under their control that will get us the rest of the way into compliance with the federal health standards. Our local Air Board blames everyone except themselves. They claim the EPA rules are unfair and cry that local polluters have already done all that should be expected of them to clean up their crap. Industry spokesmen whine that a few lost jobs due to the expense of pollution controls are far more important than the health of millions of valley residents.

One major area where the local Air Board could do much better without incurring the wrath of industrial polluters is by eliminating the fine particulates in the smoke from wood stoves and fireplaces. The air district has partially regulated wood fires by setting pollution level thresholds above which burning is not allowed. They have also provided monetary incentives for people to switch older wood stoves for cleaner ones certified by EPA. This has actually been a monetary windfall for local stove and hearth dealers but it has not cleaned our air.

Here is the problem. These certified stoves are advertised as four or five times cleaner than the older ones but they are still filthy when compared to other sources of heat such as natural gas or electricity. Natural gas heating a home is nearly 200 times cleaner than a properly working certified wood stove. CARB is actually encouraging a switch to electric heating because of the greenhouse gas emissions from natural gas. In response, some people claim that burning wood is carbon neutral but that is false on several levels. The common almond wood grew from the utilization of huge amounts of fossil fuel based inputs such as fertilizer and water pumping. Also, the black carbon in wood smoke is a greenhouse gas far worse than carbon dioxide and totally negates any carbon neutrality equated with burning wood.

The air district claims these new stoves are really clean but the reality is far different. For a certified stove to be as clean as advertised the wood has to be in small pieces and stacked carefully leaving lots of air space. It also has to have optimal moisture levels between 5 and 15 percent. Too much or too little moisture, or the use of large pieces of wood, causes the particulate emissions to rise dramatically. These stoves also smoke when warming up and cooling down. The highest pollution levels happen when users bank the stove late at night by inserting large chunks of wood and closing down the damper allowing the wood to smolder until early morning.

The health standard for PM 2.5 is set at 12 micrograms per cubic meter. The average for the year needs to be below this level in order to meet the standard and be protective of public health. Unfortunately, we often have daily levels 5 or 6 times higher than this level in our winter air and the fall, during harvest season, is almost as bad.

Irresponsibly and irrationally, the air district allows certified stoves to burn at air pollution levels as high as 65 micrograms per cubic meter. Even the older stoves can burn at up to 20 micrograms per cubic meter. It should be obvious to the Air Board that setting curtailment levels above the standard does not make sense. The question should be asked if the Air Board is catering to wealthier wood burners who can afford the certified stoves and don’t want to be told they can’t have an old-fashioned wood fire in their homes when the air outside is filled with soot.

Another issue is enforcement of the wood burning curtailment rules. Observing smoke coming from a nearby chimney does not automatically imply a violation because, as already noted, even certified wood stoves can smoke when first lit or if operated incorrectly. At night, there is virtually no enforcement possible because the smoke is invisible.

Realistically, if you smell that sweet smoke in your neighborhood from a nearby fireplace or wood stove there should automatically be a violation. That smoke contains particulates which are harming you and your family’s health. The reason wood smoke often smells sweet is because it contains benzene, a carcinogenic.

Ironically for the wood burner, who often burns illegally on no-burn days, the air inside a home is usually more polluted with the smoke and associated poisons than a nearby neighbor’s yard. Other bad things found in wood smoke that can fill your home and your neighbor’s yard are dioxins and various tar compounds which can cause cancer, harm reproductive organs, and damage immune systems.

If the air district does not have the political strength to ban wood burning it at least needs to ban the use of non-certified stoves, ban the installation of fireplaces in new homes, and put the curtailment level at 12 micrograms instead of the current 65 micrograms. The three S-men in constant public view at the air district, Seyed, Samir, and Sheraz, need to acknowledge these issues and tell their bosses, the Air Board, that more needs to be done.


Longtime clean air advocate Tom Frantz is a retired math teacher and Kern County almond farmer. A founding member of the Central Valley Air Quality Coalition, he serves on the CVAQ steering committee and as president of the Association of Irritated Residents. CVAQ is a partnership of more than 70 community, medical, public health, environmental, and environmental justice organizations representing thousands of residents in the San Joaquin Valley unified in their commitment to improving the health of Californians. For more information, visit www.


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    The Community Alliance is a monthly newspaper that has been published in Fresno, California, since 1996. The purpose of the newspaper is to help build a progressive movement for social and economic justice.

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