Bangkok's PM2.5 Problem: How to Protect Your Indoor Air

Bangkok regularly records PM2.5 levels two to three times higher than WHO safe limits. The haze season from January to April can push readings to hazardous levels, and even on normal days, urban pollution poses a real health risk.

Most people assume staying indoors protects them. The reality is more complicated.

How Pollutants Get Inside

Pollutants enter through open windows and doors during high-pollution days, natural air infiltration through building gaps, occupants bringing particles in on clothing, cooking smoke, and VOCs from building materials.

What Your AC Does and Does Not Do

Standard split-type ACs recirculate indoor air; they do not bring in fresh outdoor air. Their basic filters, typically G4 grade, catch large dust particles but miss PM2.5, which is fine enough to penetrate deep into lung tissue. A dirty AC filter actually becomes a PM2.5 source itself, storing particles and releasing them when the fan runs.

What Actually Helps

Air purifiers with an H13 HEPA filter or better capture at least 99.95% of the particles that are hardest to catch, which covers PM2.5, bacteria and mold spores. Size them for your room area. ERV and HRV ventilation systems bring in filtered fresh air while recovering energy, and Broan systems are designed for exactly this purpose. Keep windows closed during poor air quality days and check AirVisual or IQAir for real-time Bangkok readings. Service your AC filters every 1 to 2 months during haze season.

For Families with Children or Elderly

The health impact of PM2.5 is significantly higher for children under 10 and adults over 65. For these households, we strongly recommend HEPA air purifiers in bedrooms combined with a whole-home ventilation strategy.