Keeping Wildfire Smoke Out of Our Lungs
Sana Kazilbash posted on September 15, 2020 |
Record-breaking levels of particulates make air filtration imperative during the Western fires.

Rampant wildfires have applied a sepia filter to California. (Image courtesy of Curbed.)
Rampant wildfires have applied a sepia filter to California. (Image courtesy of Curbed.)

The American West is on fire, and the resulting orange skies look apocalyptic. Homes and cars are covered in what looks like gray snow—the same ash that hangs in the air and quietly blots the sun out of the sky. The hellish landscape feels unsettling, and vaguely gives one the notion of having walked into a scene out of a Hollywood movie. Reality feels different.

Over the last several weeks, wildfires have been incinerating thousands of homes in the states of California, Oregon and Washington. More than five million acres of desiccated forests have been scorched. In California, so far 26 times more territory has been destroyed by wildfire than the same time last year. Millions of Americans in major cities, including Los Angeles, San Francisco, Portland and Seattle, are being left to breathe some of the worst air quality recorded worldwide. The smoke is even beginning to travel as far as the province of Alberta in central Canada.

“We haven’t had anything ever this close,” says Margot Cooper, a resident of Oregon where the blazes are approaching areas that haven’t seen wildfires for decades. “It’s the first time it’s literally in our backyard.”

As though concerns about your house being set ablaze by nature aren’t bad enough, smoke inhalation has been found to be responsible for the majority of deaths related to fires.

“Smoke inhalation is suspected to be the cause of 75 percent of all fire-related deaths in the U.S.,” states pulmonologist Dr. Sumita Khatri, co-director of the Asthma Center at Cleveland Clinic. Fatalities stem from “a lack of oxygen to the arteries that supply the heart with oxygen and lack of oxygen delivery to essential organs.”

What’s in Smoke?

Smoke consists of heated particles and gases. The composition of smoke varies based on the materials being burned, the temperature of the flame and the amount of oxygen available to the fire. For example, incomplete combustion during the burning process can create toxic gases—the most common of these is carbon monoxide, which is deadly even in small quantities because it replaces oxygen in the bloodstream.

The combustion of synthetic materials such as PVC, rubber and foam results in hydrogen cyanide, which interferes with cellular respiration and potentially leads to cardiac arrest. Burning vinyl household products forms phosgene, which at high levels can cause pulmonary edema and subsequent death.

Particles in smoke include unburned, partially burned and completely burned substances which can be tiny enough to penetrate the respiratory system’s protective filters and become embedded in the lungs, causing inflammation and oxidative stress. While some particles can be irritating to the eyes and digestive system, others are actively toxic . Smoke also carries lethal vapors that can poison humans if inhaled or absorbed through the skin.

In the case of a house fire, a blaze can quickly incapacitate or kill the occupants by asphyxiation—either by consuming the available oxygen, or by displacing it with other gases such as carbon dioxide. Superheated gases can burn the airways in a person’s respiratory tract, while the irritant compounds in smoke, including sulfur dioxide, ammonia, hydrogen chloride and chlorine, can cause swelling and airway collapse.

The effect of decreasing oxygen levels. (Image courtesy of National Fire Protection Association.)
The effect of decreasing oxygen levels. (Image courtesy of National Fire Protection Association.)

Wildfire smoke is known to contain additional air pollutants such as fine particulate matter with an aerodynamic diameter of less than 2.5 μm (PM2.5), ozone, polycyclic aromatic compounds and nitrous oxides. When it comes to wildfire smoke, the fine particulate matter is the primary pollutant of concern due to its abundance.

For example, the World Health Organization’s (WHO’s) recommended safe limit for PM2.5 is 10 μg/m3. In comparison, the U.S. wildfires this year have reached PM2.5 levels of an unimaginable 453 μg/m3.

(Image courtesy of U.S. Environmental Protection Agency.)
(Image courtesy of U.S. Environmental Protection Agency.)

Numerous studies have linked wildfire smoke to serious respiratory, cardiovascular and cerebrovascular problems. One analysis demonstrates an increase in the rate of hospital visits during wildfire season. Another study investigating the extensive 2015 wildfire season in California shows that emergency department visits went up on days with dense smoke plumes—with patients experiencing health issues including asthma, chronic obstructive pulmonary disease (COPD), bronchitis, pneumonia, heart attacks and strokes.

The health effects of exposure to wildfire smoke don’t disappear when the skies are finally clear, either. According to a June 2020 study, bad fire seasons are often followed several months later by flu seasons three to five times worse than usual.

“Decades of research have shown that elevated air pollution exposure is associated with a number of adverse health impacts, including compromised immune systems,” explains Dr. Erin Landguth, an associate professor of public and community health science at the University of Montana.

Children, pregnant women, older adults and individuals with existing heart or lung diseases are particularly vulnerable to wildfire smoke. According to Dr. Sarah Henderson, senior scientist at the British Columbia Center for Disease Control, smoke exposure could have lifelong health implications for babies.

“[Wildfire smoke] may do damage to the developing lungs that they may never recover from,” says Dr. Henderson. After all, young children breathe more air per pound of body weight than adults.

The coronavirus pandemic further complicates the impact of the wildfires. People with COVID-19 may be at increased risk of health effects from smoke exposure due to their already compromised cardiovascular function. This goes both ways; the Centers for Disease Control and Prevention (CDC) states that wildfire smoke can irritate the lungs, cause inflammation, alter immune function and increase susceptibility to respiratory infections, including COVID-19.

What Can You Do to Protect Yourself?

For starters, avoid going outside, and stay updated on public health messages about safety measures. If you absolutely must leave your home for essential activities, visit to find reliable information about wildfire smoke and the Air Quality Index (AQI).

Look for a well-fitted N95 or P100 respirator marked “NIOSH” (National Institute of Occupational Safety and Health). While cloth masks are considered helpful in slowing down the spread of COVID-19, they offer little protection against wildfire smoke due to their inability to filter out the tiny particulate matter present in wildfire smoke. Dust masks are also insufficient, as they are designed to trap larger particles such as sawdust. Tissue is also ineffective, since it allows wildfire smoke to seep through.

Instructions for wearing a respirator. (Image courtesy of
Instructions for wearing a respirator. (Image courtesy of

Unfortunately, the recommended N95 masks are currently in short supply due to the COVID-19 pandemic. If you don’t own one, Dr. Henderson suggests making your own tight-fitting masks from different layers of fabrics—“particularly tightly woven cotton and silk together”—as a last resort.

The best option would be to move away from areas with thick smoke, but if this isn’t possible then one should stay indoors and reduce activity.

When at home, keep windows and doors closed and run air conditioners in recirculation mode (“On” rather than “Auto”) so that outside air isn’t being drawn into your home. Maintain indoor air quality by avoiding smoking, burning candles, using aerosol products and cooking on gas or wood-burning stoves. Avoid frying food, as well, since this can increase indoor smoke. You should even refrain from vacuuming, which stirs up particles already present inside your home.

The U.S. Environmental Protection Agency (EPA) has a number of recommendations for indoor air filtration. One option includes upgrading your central air system filter to a Minimum Efficiency Reporting Value (MERV) rating of 13 or higher, in order to reduce indoor particles by as much as 95 percent.

Portable air cleaners can save on the cost of continuously operating an enhanced central system. When these self-contained filtration appliances are fitted with high efficiency filters, they can reduce indoor particle concentrations by up to 85 percent depending on factors including the size of the air cleaner, area to be cleaned, filter efficiency and fan speed.

Air cleaner size recommendations. (Image courtesy of EPA.)
Air cleaner size recommendations. (Image courtesy of EPA.)

The Clean Air Delivery Rate (CADR) of a portable air cleaner is the removal efficiency for a specific size particle and volume of air delivered in one minute. The Association of Home Appliance Manufacturers website provides useful information on appropriate air cleaner sizes for an intended area. The higher the CADR, the more particles the air cleaner can filter. According to the EPA’s guide to home air cleaners, activated carbon filters can be additionally effective for removing the gases present in smoke.

It is recommended to invest in a portable air cleaner that costs more than $200, as cheaper models may not be useful in protecting against wildfire smoke.

The two types of portable air cleaners are mechanical and electronic. Mechanical air cleaners are known to be reliable and ozone-free, while electronic ones pose an ozone hazard and should be selected with caution.

Electrostatic precipitators (ESPs) are one of the main types of electronic air cleaners. (Image courtesy of Encyclopedia of Plasma Technology.)
Electrostatic precipitators (ESPs) are one of the main types of electronic air cleaners. (Image courtesy of Encyclopedia of Plasma Technology.)

Ozone and “hydroxyl” generators should be avoided due to the harmful chemicals that they emit into the air. A list of California’s certified ozone-safe air cleaners can be found here.

This Is Only the Beginning

Unfortunately, for much of the western U.S., the peak wildfire season is only just starting.

(Image courtesy of British Columbia Center for Disease and Control.)
(Image courtesy of British Columbia Center for Disease and Control.)

Wildfire season in North America has increased in intensity and duration, and climate change appears to be a big reason. Reduced summer precipitation and heightened temperatures have led to a rise in the frequency and spreading speed of wildfires.

“Warmer and drier conditions create drier fuel,” says Dr. Philip Duffy, a climate scientist and president of the Woodwell Climate Research Center. “What would have been a fire easily extinguished now just grows very quickly and becomes out of control.”

Perhaps the autumn rains of October and November can provide relief? Alas, even these are delayed—thanks to the accelerating climate change.

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