Classification index
Hazardous (AQI 301+)
Summary: Emergency conditions where serious health effects are likely for everyone.
Health implications
Rapid symptom onset is possible across all groups. Exposure should be minimized immediately.
Recommended actions
- Stay indoors and avoid non-essential outdoor activity.
- Use sealed and filtered indoor environments where available.
- Follow emergency/public health advisories closely.
For schools and workplaces
Suspend outdoor operations and activate emergency continuity procedures until conditions improve.
Emergency Conditions: Stay Inside
AQI above 300 means emergency conditions — rapid symptom onset is possible for everyone, and exposure must be minimized immediately.
Stay indoors and avoid all non-essential outdoor activity. Use sealed, filtered indoor environments wherever possible — close all windows, run HVAC with a MERV-13 filter, and consider a portable HEPA unit. Follow emergency and public health advisories closely. Schools and workplaces should suspend outdoor operations and activate emergency continuity procedures.