Air quality for asthma

Last updated 2026-05-23 · This page is for general information and is not medical advice.

If you have asthma, the standard AQI categories aren't your action thresholds — yours land roughly one color earlier. This page covers the pollutants asthmatics react to first, the AQI thresholds the CDC and the American Lung Association actually recommend for asthma management, and the specific overlap between bad-air days and rescue-inhaler use.

The pollutants asthma reacts to first

Asthma is fundamentally a chronic inflammation of the airways. Three of the six EPA criteria pollutants disproportionately drive asthma symptoms:

Each acts through a slightly different mechanism, which is why the AQI dominant-pollutant displayed in the app matters for asthma management — a day at AQI 100 driven by ozone is different from a day at AQI 100 driven by PM2.5.

• PM2.5 (fine particulate) — bypasses the upper-airway defenses and deposits in the deep lung. Drives the largest asthma-ED-visit signal during smoke events. The single most-important pollutant to track if you have asthma.
• Ground-level ozone — irritates the airways directly. Asthma response is dose-dependent and often felt within an hour of moderate-intensity outdoor activity. Peak ozone is summer afternoons in sunny metros.
• NO₂ (nitrogen dioxide) — both ambient (near busy roads) and indoor (gas stoves, gas furnaces). Closely correlated with asthma exacerbations in children. See NO₂ and gas stoves.

Action thresholds — one color earlier than the general public

The EPA's standard AQI sensitive-groups category starts at Orange (101–150). For asthmatics, that's your action threshold, not your awareness threshold. A practical action plan:

• Green (0–50) — Normal activity. No action.
• Yellow (51–100) — Awareness. Check forecast for the day; rescue inhaler within reach.
• Orange (101–150) — Reduce prolonged outdoor exertion. Shift outdoor exercise indoors. Premedicate per your asthma action plan if your doctor has prescribed pre-exercise bronchodilator use.
• Red (151–200) — Avoid outdoor exertion entirely. Close windows. Run HEPA filtration in the room you spend most time in. If you use a peak-flow meter, expect lower readings.
• Purple+ (201+) — Indoor only. If symptoms escalate despite rescue inhaler, contact your clinician. ER threshold drops on hazardous-AQI days for asthmatics.

Wildfire smoke and asthma

Wildfire-smoke days are the worst-case scenario for asthma management. ED visits for asthma rise sharply at AQI 100+ during smoke events — meaningfully higher than at the same AQI driven by typical urban PM2.5, because smoke particles are smaller and contain more reactive organic compounds.

The protections that genuinely work are covered in detail in our Wildfire Smoke guide and the Corsi-Rosenthal box guide. The asthma-specific additions:

• Have a 5-day supply of rescue inhaler before smoke season starts (June–November in most western states).
• Replace your HVAC filter with MERV-13 before fire season. Change it twice as often during active smoke days.
• Use a HEPA purifier sized for the bedroom (see Air purifier sizing). A bedroom you can sleep through the night in clean air is the single highest-leverage thing.
• During the smoke event, run errands at first light when smoke has often subsided overnight, not afternoon when concentrations peak.

Indoor air and asthma

Most asthmatics spend 70–90% of their time indoors, so indoor air management often matters more than outdoor AQI. The big indoor asthma drivers:

• Gas stoves — meaningful NO₂ source. Range-hood ventilation cuts the kitchen NO₂ peak by half. See NO₂ and gas stoves.
• Wood-burning fireplaces — high indoor PM2.5. Avoid during asthma season.
• VOCs — paints, cleaners, scented products, new furniture off-gassing. See VOCs at home.
• Dust mites, mold, pet dander — outside the criteria-pollutant AQI but still asthma triggers. HEPA filtration helps with all three.

Tools that pair with this

Smog Report shows real-time AQI from official reference monitors near you, with the dominant pollutant labeled — so you know whether today's 110 is driven by PM2.5 (smoke or traffic) or ozone (heat + sun). For an asthmatic, the dominant pollutant changes the mitigation. The iOS app supports widgets and Lock Screen alerts that fire when AQI crosses your personal threshold.

For the joint AQI + respiratory-illness picture during flu/RSV/COVID season — particularly relevant if you have asthma — see our AQI and outbreaks guide and Pandemic Watch.

What this page is not

This is not medical advice. Action thresholds here are general; your personal asthma action plan should be developed with your clinician and may be tighter or looser depending on severity, medications, and recent exacerbation history. If you don't have a written asthma action plan, the American Lung Association and AAFA both publish templates worth bringing to your next appointment.

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