shows a fire in a fireplace
Source: US Department of Energy

By Catherine Clabby

In the darkest and coldest winter nights, few things can bring more cheer than sitting in front of a big fire.

But for some, it can do harm.

Wood smoke, indoors and out, can be hazardous to people living with asthma and other chronic health problems, something Kiana Redd saw while growing up in Wake County.

Her mother, a nurse, gave up on trying to light a fire in their family home. Every time she did, two brothers with asthma would start coughing and have trouble stopping.

Redd, the Healthy Homes program coordinator in Orange County, now understands why.

“Wood smoke is an irritant for someone with asthma, just as much as cigarette smoke. Sometimes worse,” said Redd, who is trained in detecting health hazards in homes and educating families on how to reduce them.

The ways in which wood smoke poses environmental health risks are better understood than ever before. Luckily so are the steps to prevent harm.

Downsides to smoke

Wood smoke is much more than that whiff of something pleasant in the air. It’s a combustion emission whose plumes carry a complex mix of gases and particles into the air.

The gases can include unhealthy benzene and formaldehyde and the particles can be small enough to be classified as particulate matter. The smallest particles — those with diameters of  10 micrometers or below — can travel deep into people’s lungs and stir trouble.


To those with asthma and other lung conditions, exposures to wood smoke for hours or days can aggravate their disease. Along with lung and heart disease sufferers, children, teenagers and older adults are also susceptible to adverse effects from wood smoke, according to the EPA.

Emerging research is finding that people who are obese or have diabetes are also more likely to experience shortness of breath, tightening in the chest, wheezing or coughing from exposure.

So before lighting a fire, it’s important to consider who will be exposed to the smoke.

shows a man in a white coat examinging a test tube
David Peden, Professor in the Department of Microbiology & Immunology, UNC School of Medicine. Photo courtesy: UNC Children’s Hospital Twitter account

“If you are using a recreational fireplace for ambiance, I’d argue you might be very selective when you do that,” said David Peden, a pulmonologist and director of the Center for Environmental Medicine, Asthma and Lung Biology at the University of North Carolina at Chapel Hill medical school.

The EPA recommends that people burn only dry, split, well-seasoned wood, which burns more efficiently, and promptly clean up ash from a fire.

A properly functioning flu and a clean chimney is essential. Keeping fireplace glass doors closed limits where emissions can move. Outdoor temperatures are important too, Peden said. Colder temperatures improve how well the flue draws fumes up and away from the flames.

“If you’re having a fire in fireplace and it’s 55 degrees outside, it’s not going to vent well,” he said. “You get good venting when it’s 25 degrees outside.”

Outdoors too

Public health experts are also paying increasing attention to health risks from wildfire smoke. For one, these events are expected to increase as global temperatures continue to rise with climate change.

This is not an abstraction in North Carolina. Thirty fires scorched 80,000 acres in drought-stricken counties in western counties in October and November 2016, the worst rash of fires on record. The resulting smoke particle pollution locally reached levels dangerous to everyone, not only people with compromised health.

Meteorological conditions produced an inversion layer: warm air trapped dense, colder air near the ground, slowing the smoke’s dispersal, especially from valleys and other lower ground.

shows satellite image of western NC, with smoke from wildfires being blown east and south
From their orbit high above Earth, NASA satellites captured images of the wildfires that erupted in the Southeastern US. This image was taken in August of 2016.

Peden, the UNC pulmonologist and researcher, is among the scientists trying to better understand the biology that produces some people’s ill health effects from wood smoke. They are also looking for ways for firefighters and others to protect themselves from the hazards.

In specially designed chambers in Chapel Hill, his research team and colleagues conduct studies where people exert themselves on stationary bikes while exposed to wood smoke generated by wood stoves.

The researchers are exploring the effects of a gene that seems to influence a person’s  reaction to wood smoke. They are also testing whether a type of the nutritional supplement vitamin E (gamma tocopherol) can reduce inflammation in airways that exposure to wood smoke can produce.

If it works, a new treatment might be in the works to help people with asthma, and those without it.

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Catherine Clabby

Catherine Clabby (senior environmental reporter) is a writer and editor. A former senior editor at American Scientist magazine, Clabby won multiple awards reporting on science, medicine and higher education...

2 replies on “When Wood Smoke Poses Risks”

  1. People just forget that fireplaces consumes a lot of indoor oxygen that the oxygen content indoors plummet to brain damaging levels if residents stay indoors for extended periods of time. maybe low indoor oxygen content can lead to brain damage like Alzheimer’s disease or dementia as well as many other diseases like Parkinson’s disease perhaps.. All the good the medical guys can do with more advanced medicine to treat your brain diseases… Prevention is the way to go… Ban firewood now! do research on whehter my theory is correct. Oxygen is important to brain’s health. 21% oxygen is found in normal atmopshere.. Indoors can plumet to single digit levels which is not good !
    keep your emotions aside and face the evils fo firewood ! Own up to that!

    1. Can you provide evidence of your statement:
      “Indoors [O2] can plumet to single digit levels which is not good !”
      I have been researching of the health dangers of burning wood for ten years, and have not known of this. Please provide a link? thanks.

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