The haze condition in Singapore worsens especially on yesterday when the Pollutant Standards Index (PSI) breached hazardous level. PSI is used and well known in Singapore as an air quality descriptor. Another important descriptor not to be over-sighted is the PM
2.5 level which is a dominant pollutant during haze episodes. The smaller PM
2.5 particles can pass through the smaller airways and travel deep into the lungs.
How do we interpret PM
2.5 and at which level should we be cautious?
| PM2.5 (µg/m3) | PSI (Singapore) | Health Concerns |
| 0 - 12 | 0 - 50 | Good |
| 12.1 - 35.4 | 51 - 80 | Moderate |
| 35.5 - 55.4 | 81 - 100 | Unhealthy for sensitive groups |
| 55.5 - 150.4 | 101 - 200 | Unhealthy |
| 150.5 - 250.4 | 201 - 300 | Very unhealthy |
| 250.5 - 350.4 | 301 - 400 | Hazardous |
| 350.5 - 500.4 | 401 - 500 | Very hazardous |
