PM2.5 Safe Levels in India: WHO vs CPCB
The WHO’s 2021 PM2.5 guideline is 15 µg/m³ for a 24-hour average and 5 µg/m³ for an annual average. India’s 2009 national ambient standards specify 60 µg/m³ and 40 µg/m³, respectively. Always compare readings over the same time period.
If you are checking a home monitor, start with the concentration in µg/m³, the averaging period and the room measured. An AQI colour or a single low reading does not tell the whole story.
WHO guidelines and India’s ambient standards
| Reference | Annual average | 24-hour average |
|---|---|---|
| WHO air quality guidelines, 2021 | 5 µg/m³ | 15 µg/m³ |
| India NAAQS, 2009 | 40 µg/m³ | 60 µg/m³ |
WHO’s short-term guideline uses the 99th percentile of daily averages, equivalent to about three or four exceedance days a year. It is not a promise of zero health risk below a threshold. The WHO guideline and India’s regulatory ambient standard serve different purposes; neither certifies an individual home from a spot measurement. See the WHO guideline explanation and CPCB’s national standards.
Is PM2.5 of 15, 35 or 60 safe indoors?
First ask whether the number is an instantaneous reading or a daily average. A monitor showing 10 µg/m³ for a few minutes cannot establish the room’s 24-hour average. Likewise, a short cooking spike is different from a high concentration maintained all day.
Use the guideline as a reference for reducing exposure, rather than labelling an entire day safe from one number. Save the daily history, identify recurring peaks and compare similar days before and after making a change.
AQI is not the same as PM2.5 concentration
AQI is an index, while µg/m³ measures particle concentration. Different countries use different AQI scales. India’s overall AQI can also be driven by a pollutant other than PM2.5, so the overall number alone cannot uniquely identify PM2.5. Check the pollutant and scale in the app. CPCB’s National AQI information explains the Indian system.
For a useful home comparison, record PM2.5 in µg/m³ rather than comparing colours from two apps.
A practical home measurement routine
- Choose the room you use most, then follow the monitor manufacturer’s placement and calibration instructions.
- Keep the monitor in the same place for each comparison. Record its model and any settings you change.
- Log a full day, including cooking, occupied evenings and overnight use. Note open windows, purifier settings and cleaning activities.
- Compare daily averages and recurring peaks over several days. Also record outdoor conditions so a cleaner day is not mistaken for better equipment performance.
- After a change, repeat the same routine. Keep the original readings rather than relying on a single before-and-after photo.
This is a suggested comparison method, not a regulatory certification procedure. Consumer measurements are most useful when their limitations and conditions are recorded.
Reducing particles at home
Start by reducing indoor pollutant sources and using suitable kitchen exhaust. Ventilation with clean outdoor air and appropriately sized particle filtration can complement those steps. A filter cannot remove every indoor pollutant. The US EPA’s home air-cleaner guide explains these complementary measures.
For product selection, compare room size, airflow at the speed you will actually use, noise and maintenance. A room purifier and a filtered fresh-air system serve different needs: consider whether you need particle removal in one room, outdoor-air supply, or both.
Frequently asked questions
Does a low PM2.5 reading mean the room is well ventilated?
No. PM2.5 and ventilation need separate assessment. Read our bedroom CO₂ guide to understand what a CO₂ measurement can and cannot show.
Should I compare my indoor reading with the nearest outdoor station?
It is useful context, provided you record matching times and units. It is not a calibration test: the station and your room measure different places under different conditions.
How do I choose between a room purifier and a whole-home system?
Start with the spaces you want to treat and whether you also need filtered outdoor-air supply. Review the aqi0 whole-home air purifier, system specifications and pricing before arranging a layout assessment.
Discuss your home’s air quality
Share your floor plan and any monitor history with aqi0. We can assess the intake location, airflow route and system sizing for your home. The whole-home air purifier is ₹82,600, fully installed; the optional AQI/PM2.5 monitor is ₹4,000, sold separately.