What to know about air quality during wildfire season

Updated Sept. 13, 2021

If you step outside in Northern California during wildfire season, you can often tell that the air quality isn't great. Wildfires throughout the state continue to burn stronger and longer, making it hazardous to be outdoors in some areas while filling the sky with smoke. 

California has always had wildfires, said Cort Anastasio, professor in the Department of Land, Air & Water Resources at UC Davis. But the extent to which they’ve been happening now is much greater. 

“Our summer air quality now is much worse than it was in the past,” he said. 

That can make air quality extremely hazardous. 

But how can you tell when air quality is harmful? And if it is, what should you do? Here are tips from experts about checking air conditions and protecting your health.

How do I know what the air quality is for my area?

Each day it’s smoky outside, you should check an air quality index (AQI), either at Sacramento’s Air Quality Management District website or the Environmental Protection Agency’s site, airnow.gov. That will show if there’s an unhealthy amount of pollution in the air where you live. 

The current air quality index forecast in the Sacramento region. The colors correspond to the level of risk.

The AQI is usually calculated based on five major air pollutants: ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide and nitrogen dioxide. Each is measured and weighted differently and then combined into a single value — the AQI. 

In the U.S., these air quality measurements range from 0 to 500, with 500 being the most harmful. Any measurement below 100 isn’t likely to affect your health. 

Dr. Kent Pinkerton, director of the UC Davis Center for Health and the Environment, said that people with pre-existing respiratory or heart conditions start to be adversely affected with measurements above 100. 

“When the AQI goes above 151, that’s unhealthy for everyone,” he said. “It would just simply not be a good idea to be doing any outdoor activity, whether it be exercising, walking, that sort of thing.” 

Why doesn't the AQI match what I see?

Sometimes air quality measures may not seem to match what we can see when there is heavy smoke or even ash in the air.

One reason is that smoke and haze can be visible in the air even if it's not at ground level, says Thomas Wall with the Sacramento Air Quality Managment District. 

"That's one are where we see folks who look at current conditions and may see it looks OK, but it's gross looking and dark outside," Hall says. "That doesn't necessarily mean that pollution is at the ground level."

airnow.gov

Still, Hall cautions that there can be big differences in air quality even between neighborhoods. While checking local air quality measures is a good first step, use caution if you can see or smell smoke.

"If you're smelling smoke you're definitely breathing it," Hall says. "It doesn't mean necessarily it's unhealthy, but it's a good indicator it is."

Why does the AQI for my area look different on different websites? What’s most reliable?

Different websites and companies use different methodologies for reporting air quality, according to Amy McPherson, the public information officer for the California Air Resources Board.

“Different sources have different time delays in reporting information, create AQI averages using different time periods and some are integrating many data sources other than just PM measurements (i.e. land use data, satellite, meteorology),” she wrote via email. 

CARB recommends using the AirNow Fire and Smoke Map to look at air quality during wildfire season. It’s run and maintained by the EPA and includes data from several sources. Some of those sources include air monitoring equipment owned and maintained by federal and local air districts; those average AQI over 24 hours and update it around every hour. Another one of those sources is PurpleAir sensors, which average AQI over 120 seconds. 

"PurpleAir sensors typically read higher than the actual AQI, so the data quality can be questionable,” McPherson wrote. “However, they update every few minutes, so they can be a valuable resource during a wildfire, when air quality can change by the minute. EPA worked with PurpleAir to develop an algorithm to adjust the sensor data on the Fire and Smoke Map, so it will be more consistent with other monitoring sources.”

PurpleAir sensor data is also mapped here, and you can look at data by neighborhood update in real-time. You can apply the “US EPA” filter under the Conversion drop down menu to see AQI corrected for the varying masses of wildfire and woodsmoke particles.

How does breathing in wildfire smoke affect your health?

Wildfire smoke contains a complex mixture of organic chemicals including carbon dioxide, carbon monoxide and hydrocarbons, plus water vapor, particles, nitrogen oxides and trace minerals. The main concern with smoke is “fine particles” — tiny bits of matter that you can inhale deeply into your lungs. 

Those fine particles can affect your lungs and your heart. They irritate your respiratory system, and exposure to high concentrations can cause persistent cough, phlegm, wheezing and difficulty breathing — even for healthy people.

“A rapid heartbeat, a tightness in your chest or chest pain would be other signals that the air quality isn’t good,” Pinkerton said. 

Studies have also found that short-term exposure to these fine particles over days or weeks can aggravate pre-existing heart and lung disease. Recent studies have also shown that wildfire smoke can worsen COVID-19 cases.

Are some people more affected than others?

Not everyone exposed to smoke will experience health problems. Different factors determine individual susceptibility — including your age and whether you have pre-existing lung or heart conditions, like asthma, COPD or heart disease. 

Most healthy people will recover quickly from smoke exposure, but “sensitive groups” (we hear this term a lot) may experience more acute or longer lasting symptoms.

Experts say that “sensitive groups” include children, elderly people, pregnant women and anyone who has a pre-existing heart or lung disease. 

How long do I have to worry about wildfire smoke? 

Only for as long as the fire is still burning enough fuel to produce significant smoke.

While particles can travel a long distance, like California wildfires polluting downwind all the way to the east coast of the U.S., they will eventually come out of the atmosphere and deposit on the ground, Anastasio said.

The amount of smoke, topography and weather can affect how long the smoke stays in the atmosphere and in ground-level air quality (the air we breathe), though. 

“If the conditions are right, winds can carry the smoke high enough in the atmosphere that it doesn’t affect ground-level air quality,” McPherson said. “Conversely, other weather patterns can keep it from clearing out for extended periods of time.”

What should people do when the air quality is poor?

If the air quality near you is poor, stay inside with the doors and windows closed and limit your physical activity. During exercise your air intake increases, which brings more pollution deep into the lungs. Experts say staying inside and reducing physical activity can reduce exposure by at least a third or more.

You can also upgrade your air conditioner filters, or buy a portable air cleaner. If you have a central air conditioning system in your home, set it to re-circulate or close outdoor air intakes to avoid drawing in smoky outdoor air. CARB has more information on how to keep the air inside your home clean on its Smoke Ready California web page.

Other options to get a break from the smoke include going to public libraries, hospitals, movie theaters and other public buildings with good HVAC systems. If conditions are going to be bad for a long time, you might consider going to stay with a friend or family member where the air quality is better.

Masks can be helpful, but you should reduce your exposure in other ways first — namely by reducing activity and staying indoors.

If you have to go outside, how can you best protect yourself?

If you’re driving, make sure your windows are rolled up and set the air conditioning in your vehicle to Recirculate mode to avoid bringing the smoke into your vehicle. 

Wearing a N95 or KN95 mask will help filter out the particles from the air that you’re breathing when outside, and have the added benefit of protecting against COVID-19 particles. 

“People seem to think the surgical masks with cloth masks that work to keep coronavirus at bay also work for smoke,” said Anastasio. “By and large, smoke particles tend to be smaller than virus particles, so if it’s a smoky day and you go out with your surgical mask on, it’s not really making much of a difference at all.” 

When looking for a N95 or KN95 mask, make sure it fits your face and has a proper seal around your nose and mouth to prevent particles from coming into the mask. This page will guide you through the process of doing a seal check. 

You can find N95 or KN95 masks online or at stores that carry medical supplies.