Air quality guides
Plain answers about the AQI, wildfire smoke, air purifiers, furnace filters and ozone, checked against EPA, CDC and state health agency sources.
What the Air Quality Index numbers and colors mean
How to read the AQI, from green to maroon, who counts as a sensitive group, PM2.5 versus ozone, why the live number moves, and what changed in 2024.
Read the guide →How to protect yourself from wildfire smoke
What wildfire smoke does to your body and how to cut your exposure at home, outdoors and in the car, with advice for kids, pets and when to leave.
Read the guide →How to choose an air purifier for smoke
How to size an air purifier by its smoke CADR, which labels to trust, which technologies to skip, and what filters, power and noise cost you over time.
Read the guide →How to use your furnace or AC filter against smoke
What MERV ratings mean, why the EPA points to MERV 13 for smoke, how to set your thermostat fan, and how often to change the filter when it's smoky.
Read the guide →How to make a box fan air filter for wildfire smoke
How to build a box fan filter or a Corsi-Rosenthal cube, what EPA lab tests found, which fans to use, and how often to change the filters.
Read the guide →What ozone pollution is and how to avoid it
Why ground-level ozone peaks on hot, sunny afternoons, what it does to your lungs according to the EPA, and how to time your outdoor activity around it.
Read the guide →Kids, school and bad air: what each AQI level means
What school guidance says about recess, PE and sports at each AQI color, the symptoms to watch for in kids, and how to plan for smoke and ozone days.
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