At a glance
Your quick answer
The practical decisions most people need to make when the AQI reaches 120.
- AQI
- 120
- Category
- Sensitive groups
- Outdoor exercise
- OK for most, shorten if sensitive
- Running
- Reduce distance and pace
- Children
- Limit long play
- Older adults
- Limit exertion
- Asthma
- Reduce outdoor time
- Heart disease
- Avoid strenuous activity
- Pets
- Shorter walks
- Windows open
- Only off-peak
- Air purifier
- Recommended
- Mask
- Optional for sensitive groups
AQI scale
120 sits in the Unhealthy for Sensitive Groups range
The AQI runs from 0 to 500. A value of 120 is the first band where health guidance applies to real groups of people rather than only the unusually sensitive. At 120 it sits squarely in the middle of the Unhealthy for sensitive groups band.
The meaning
What does AQI 120 mean?
What AQI measures
AQI translates pollution levels into one health-focused number. The higher the number, the greater the potential health concern.
Why 120 is Unhealthy for Sensitive Groups
AQI 120 falls between 101 and 150. Members of sensitive groups may experience health effects; the general public is less likely to be affected.
What drives the number
At this level PM2.5 is usually the culprit — fine particles small enough to reach deep into the lungs and cross into the bloodstream.
Who counts as a sensitive group?
Children and teenagers, adults over 65, pregnant women, and anyone with asthma, COPD, other lung disease, heart disease or diabetes. Outdoor workers and endurance athletes also belong here, because they breathe far more air per hour than everyone else.
Personal guidance
Is AQI 120 safe for you?
The general population is mostly unaffected at this level, but the guidance below matters for roughly one person in four.
General population
Normal activity is fine. Only unusually long or intense sessions are worth trimming.
Children
Keep outdoor play going but shorten it, and move PE or sports practice indoors if you can.
Pregnant women
Keep outdoor time short and avoid busy roads at rush hour.
Older adults
Walk rather than run, and take the session indoors if you feel breathless or unusually tired.
Asthma
Carry your reliever, pre-medicate if that is your plan, and move workouts indoors.
COPD
Stay indoors for long stretches and keep windows shut during the daily pollution peak.
Heart disease
Avoid strenuous outdoor exertion. Chest discomfort, palpitations or unusual fatigue mean stop and seek advice.
Pets
Shorter walks. Flat-faced breeds and older animals feel this level before other dogs do.
Plan your day
Outdoor activity guide
At AQI 120, healthy adults can still train outdoors but should keep it shorter. Sensitive groups should move intense activity indoors.
| Activity | Recommendation |
|---|---|
| Walking | Safe |
| Running | Shorten; sensitive groups indoors |
| Cycling | Avoid busy roads |
| Football | Shorten and add breaks |
| Hiking | Fine at an easy pace |
| Gardening | Safe |
| Outdoor work | Rotate breaks indoors |
At home
Indoor recommendations
Open windows?
Only off-peak
At AQI 120, ventilate in the early afternoon when pollution usually dips, and keep windows shut through the morning and evening peaks.
Use an air purifier?
Recommended
A True HEPA unit sized to the room makes a measurable difference at this level, especially in bedrooms.
Run ceiling fans?
Yes
Fans help a purifier mix the room, but on their own they move particles around rather than remove them.
Vacuum?
Yes, HEPA only
A non-HEPA vacuum re-suspends the fine dust you are trying to remove. Damp-mop hard floors instead.
Dry clothes outside?
Better indoors
Fabric picks up particles from the air; indoor drying avoids bringing them back inside.
Keep pets indoors?
Mostly
Keep walks short and skip the off-lead sprint until levels drop.
Do you need an air purifier?
Yes — this is the level where a purifier starts to pay for itself. At AQI 120, a True HEPA unit rated for your room size can hold indoor PM2.5 far below the outdoor reading, which matters most in the bedroom where you spend eight hours a night.
Browse recommended air purifiersDo you need a mask?
Healthy adults do not need one for short trips. Sensitive groups, outdoor workers and anyone spending more than an hour outside should wear a well-fitted N95 or FFP2. Cloth and surgical masks do not filter PM2.5.
Health effects
What you might notice
Sensitive groups are the ones who feel this band. Effects build with exposure time and how hard you are breathing.
Healthy adults
Usually nothing, though a long hard session may leave a scratchy throat.
Children
Cough, throat irritation, or getting winded sooner than usual during play.
Asthma
Higher chance of wheeze, chest tightness and needing the reliever.
COPD
Noticeably more breathless during ordinary activity.
Allergies
Eye, nose and throat irritation, worse when pollen is also high.
Heart disease
Chest discomfort or palpitations during exertion — stop and seek advice.
Simple actions
Practical tips for AQI 120
- Move hard workouts indoors or to the cleanest part of the day.
- Run a HEPA purifier in the bedroom overnight.
- Keep windows shut during the morning and evening peaks.
- Sensitive groups: carry your medication and wear an N95 for longer trips.
FAQ
AQI 120 questions, answered
Is AQI 120 dangerous?
AQI 120 is not dangerous for most healthy adults, but it is genuinely unhealthy for sensitive groups — children, older adults, pregnant women, and people with asthma, COPD or heart disease. Those groups should limit long or strenuous outdoor activity.
Can I run at AQI 120?
A healthy adult can run at AQI 120, but shorten the session and avoid busy roads — running raises the volume of polluted air you inhale several times over. If you have asthma, COPD or heart disease, train indoors today.
Is AQI 120 safe for babies?
Keep it brief. Babies breathe faster relative to their size and their lungs are still developing, so at AQI 120 limit outdoor time to short trips, avoid rush-hour roadsides, and run a HEPA purifier in the nursery.
Should I wear an N95 mask at AQI 120?
Sensitive groups and anyone outdoors for an extended period should wear a well-fitted N95 or FFP2 at AQI 120. Healthy adults making short trips generally do not need one. Cloth and surgical masks do not filter PM2.5.
Should I use an air purifier at AQI 120?
Yes. At AQI 120 a True HEPA purifier sized to the room is a worthwhile investment, particularly for bedrooms and for households with children or anyone with a respiratory condition.
Is AQI 120 unhealthy for asthma patients?
Yes. AQI 120 falls in the band named specifically for sensitive groups, and asthma is one of them. Keep your reliever accessible, follow your action plan, move exercise indoors and reduce time outside.
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