Smoke inhalation is a rapid and ruthless killer. It is the number one cause of death from fires.
I learned that lesson the hard way. Long before I was born, my Grandfather Clarke died of smoke inhalation during a fire at the Hotel Kilgore in Fordyce, Arkansas.
Wild Fires
You don’t have to be in a burning building to be exposed to large quantities of smoke. During every fire season along the Pacific Coast, vast areas come under threat of predicted hazardous smoke conditions.
The following graphic illustrates the most important factor of wildfire smoke inhalation; the size of the smoke particles. The smallest particles are inhaled deep into the lungs and cause the most lung and circulatory damage.
An Air Quality Index (AQI) and associated warnings are updated online every few hours from an EPA website. The AQI can be found for any geographical location in the U.S. based on data from air monitoring stations.
Cloth masks will not protect you from wildfire smoke.
According to the CDC, cloth masks that are used to slow the spread of COVID-19 by blocking respiratory droplets offer little protection against wildfire smoke. “They do not catch small, harmful particles in smoke that can harm your health.”
The protective capabilities offered by N95 masks are largely attributed to the masks’ certification to remove at least 95% of all particles with an average diameter of 300 nm (0.3 micrometers, or microns).
A smoke particle 2.5 microns in diameter is equal to 2,500 nm. So, in principle, the majority of smoke particles should be excluded by the 300 nm wide pores of a non-leaking N95 mask.
But the secret to success is in eliminating leaks. Inexpensive N95 masks are rarely properly worn, removing leaks around the mask. The N95 mask below, however, is specifically designed to prevent leaks on inhalation. It uses a gel seal around the face.
This particular mask has an exhalation port, thus easing exhalation breathing resistance, as do many N95 masks for the construction industry. Obviously, medical workers won’t allow patients to wear them because the patient exhales their viruses into the clinician’s face.
However, for those trying to preserve their lungs during a high smoke alert like those shown here, the masks should be ideal, though pricey.
The white filter inserts are disposable and are meant to be replaced on a regular basis once they are soiled by foreign particles.
[This writer has no tie to the manufacturer of the above masks. I was given one by a company CEO when I was working for them during the beginning of the COVID crisis. I liked it so much, I bought one for my wife.]
Even an N95 mask will not protect from some smoke particles. For instance, cigarette smoke particles have been measured to be less than 200 nm in diameter.
Clean Air in Florida
Above is the EPA AQI graphic for Panama City, Florida in September 2020. All of the following graphics were obtained contemporaneously from government websites. (I delayed publishing this post until the science article referenced at the bottom was published.)
Western Air Quality in September 2020
September 2020 was a really bad month for breathing out west, due to a multitude of wilderness wildfires. For instance, in Portland, Oregon on the morning of September 12, the AQI was near the top of the very unhealthy range.
At the same time, the AQI was near the top of the Hazardous range in Eugene, Oregon.
As seen from the data from a permanent monitor in Eugene, the air quality went from good to bad very abruptly as the smoke from forest fires spread.
The Santium Fire
As forwarned by images like that taken on September 8, 2020, Salem, Oregon was soon to come into harm’s way. The smoke from the large Santium fire had reddened the sky.
Four days later on the 12th, the AQI in Salem was literally “Beyond” bad.
The EPA warmed Everyone to stay indoors and reduce activity levels.
Visual Comparison
On August 29, 2020, the web camera onboard the R/V Oceanus based in Newport, Oregon, recorded the following image facing forward over the ship’s bow.
By noon, September 12, the AQI had increased dramatically. The AQI was 280, very unhealthy.
Visibility was nil; not from fog, but from wildfire smoke.
Science
On December 6, 2021, there was a paper published in the journal Wilderness & Environmental Medicine. The article is titled Cardiovascular and blood oxidative stress responses to exercise and acute woodsmoke exposure in recreationally active individuals. It was a laboratory study that addressed the consequences of short-term (45-min) exposures to woodsmoke during moderate-intensity cycling exercise.
The researchers expressed smoke concentration in scientific terms, micrograms of smoke particles for each cubic meter of air. To convert that concentration into EPA terms, AQI, we can use the table below, the 2012 update to the EPA’s Air Quality Index standards. It translates the conversion from AQI (second column from the left) to the concentration of woodsmoke for a 24-hour average, on the far right.
The above University of Montana researchers exposed young, active volunteers to 250 micrograms of smoke particles per cubic meter of air. If that exposure had lasted for 24-hours, it would have been at the border of the EPA’s Very Unhealthy and Hazardous AQI. But for a 45-minute exposure, no discernable physiological effects were noted.
Conclusions
Although exposure to heavy smoke and toxic vapors from fires can be immediately lethal, such exposures are relatively rare. On the other hand, multitudes of people can be exposed to woodsmoke during a particularly bad fire season, like that on the west coast from time to time.
The important takeaway from the above research is that when needed to escape from a fire area, short exposures to even Hazardous levels of woodsmoke can be tolerated. However, the emphasis is on short timeframes.
For longer exposures, tightly fitting masks like that pictured above will provide the best respiratory protection.