Pollution and Fire Dangers from Wood Stoves is Significant: Data and New Tech for Evaluation and Reduction

     It is very well known that wood smoke is toxic, especially indoors, if it is not properly vented. Wood smoke pollution is in the form of particulates and toxic gases. PM 2.5 particulates are a major wood smoke pollutant, associated with asthma attacks, respiratory illnesses, probable cancer, and other health issues. Other harmful emissions include polycyclic aromatic hydrocarbons, carbon monoxide, nitrogen oxides, methane, benzene, and formaldehyde. The EPA reported in 2016 that about 150 people die in the U.S. each year due to carbon monoxide poisoning associated with more than 17.5 million fireplaces, 241,000 hydronic heaters, and 10.1 million wood stoves nationwide, and that 65% of the wood stoves, or 6.5 million of them, are older and inefficient. They recommend replacement with EPA-certified stoves.

Benefits of replacing an old wood stove with an EPA-certified stove: 

·        saves money, fuel, time, and resources.

·        up to 50 percent more energy efficient.

·        uses 1/3 less wood for the same heat.

·        cuts creosote build-up in chimneys that helps reduce the risk of fire.

 

They also recommend using wood that has been split, stacked, covered, and stored for more than 6 months. They also note that chimney smoke, up to 70% of it, can re-enter the home or nearby homes. While they say stoves should be smoke-free inside the house, they also recommend HEPA filters, which can decrease any indoor smoke by 60%. There are cases where neighbors of someone who heats with wood have gotten respiratory diseases from wood smoke. The notion that since wood smoke is natural, it is also clean and even carbon-neutral are all wrong. Wood ovens in use at restaurants are another source of toxic wood smoke. The hipster local solar and shallow geothermal-powered café that got massive government subsidies also runs a wood oven, which likely significantly wipes out their pollution and CO2 footprints. I just noticed my neighbors, who have an extra small house to soon be inhabited by their son as he attends college, has been outfitted with a wood burner, judging from the chimney pipe. It is not too close to me and mainly downwind, so I am not too worried about it. Wood smoke kills. According to a 2022 article in Undark Magazine:

“…a 2017 study, researchers from Boston and North Carolina estimated that residential combustion causes 10,000 premature deaths in the US every year, mainly from woodsmoke.”

     Wood stoves are the U.S.'s third-largest source of particulate matter pollution, after wildfire smoke and agricultural dust. In the winter in populated areas, the use of wood stoves may be restricted as they can account for the majority of poor air quality. This is especially the case in areas where winter weather inversions are common. These inversions keep the wood smoke in the lower atmosphere where it can be breathed for a longer period and collect at higher concentrations.  

 

Chimney Fires and House Fires

     After we bought a house that was heated with a stove, fireplace, and an oil furnace in 1998, one of our first fires resulted in a chimney fire. The previous occupants had been burning pine wood, which leaves a very high amount of creosote buildup in the chimney. It had just gotten dark, and I was outside when it seemed the sky had lit up. It was the chimney on fire. Luckily, my wife was inside and immediately closed the flue, and the fire went out. After that, we had a chimney sweep come and clean the chimney. We then decided to sell the wood stove and the oil furnace and install unvented propane heaters and just have occasional fireplace fires. According to the EPA:

“The National Fire Protection Association estimates that in 2011, heating equipment was involved in an estimated 53,600 reported U.S. home structure fires, with associated losses of 400 civilian deaths, 1,520 civilian injuries, and $893 million in direct property damage. These fires accounted for 14 percent of all reported home fires.” 

The main reason for the fires was a lack of cleaning out the creosote buildup in chimneys.

 

Solutions for Cleaning Up Wood Smoke

     A recent paper published in the Journal of the Air & Waste Management Association, led by Nordica MacCarty at Oregon State University, notes that “70% of the pollution emitted from wood stove flues happens at two points in time: when a stove is first lit, and when it's reloaded.” In old stoves, heat transfer and combustion are not optimized.

"They have no catalysts or secondary combustion to reduce emissions and lower the risk of creosote buildup that can cause chimney fires."

     New methods to reduce wood smoke pollution include optimizing the amount of air in the mix and the timing of air input through automated systems. According to Tech Xplore:

“MacCarty's group is developing automated technologies that inject jets of primary and secondary air into the fire to provide just the right amount of air and mixing at the right time and place in the fire. Prototypes are showing about a 95% reduction in particulate matter emissions compared to older models, she said.

     This research can also inform the development of safer wood-burning cooking stoves, which are used extensively around the world, especially in poor countries. About 2.7 billion people around the world depend on wood stoves for cooking. This has led to many respiratory illnesses, including premature deaths. This affects women and children mostly.

"It's difficult to measure wood stove emissions in the field, so there has been relatively little in-use performance data available in the past to guide designs," MacCarty said. "Our study introduces a new system that makes collecting real-world emissions data more practical."  

     Below is a section of the paper’s abstract:

“Implications: Detailed time-apportioned PM emissions data identified conditions leading to high emission rates including startup, large loads, and operation of an uncertified stove. Provides wood stove designers insights toward optimizing performance of future stove designs, and policy makers information about the impact of user and technology on air quality objectives. Demonstrated new equipment for real-time emissions and fuel consumption monitoring that enables time-resolved PM and direct fuel mass measurements to yield better design insights for heating stoves. This method can be used by other researchers to gather much needed field measurements at a lower cost and complexity than existing methods.”

     I think the bottom line is that while an occasional wood fire is probably OK, when people heat their whole house with wood all winter, they risk their own health and their neighbor’s health, even if they have the least-polluting wood stoves. The problem is exacerbated when there are many people in small areas burning wood for primary heat. While wood can be a cheaper alternative, it is definitely not safer.

 

 

   

References:

 

New technologies help wood-burning stoves burn more efficiently, produce less smoke. Steve Lundeberg, Oregon State University. Tech Xplore. June 6, 2025. New technologies help wood-burning stoves burn more efficiently, produce less smoke

Burn Wise. Wood Smoke Awareness Kit. U.S. EPA. 2014.  Microsoft Word - Burn Wise fast facts_9.24.2014.docx

In-situ measurements of emissions and fuel loading of non-catalytic cordwood stoves in rural Oregon. Samuel Bentson, Ryan Thompson, Jaden Berger, Jonah Wald & Nordica MacCarty. Journal of the Air & Waste Management Association. May 2025. In-situ measurements of emissions and fuel loading of non-catalytic cordwood stoves in rural Oregon: Journal of the Air & Waste Management Association: Vol 0, No 0 - Get Access

An EPA fix for pollution-spewing wood stoves is backfiring. Officials are increasingly treating woodsmoke as a public health and environmental justice issue, despite opposition. Diana Kruzman / Undark. Popular Science. March 7, 2022. The health risks of wood stoves and smoke pollution | Popular Science