{
  "id": 3025007,
  "title": "ST Explains: PSI or PM2.5? What air quality measures should I refer to during the haze?",
  "url": "https://urgent.news/2026/08/24/st-explains-psi-or-pm2-5-what-air-quality-measures-should-i-refer-to",
  "topic": "culture",
  "section": "Culture",
  "published": "2026-08-24T13:10:00.000Z",
  "source": {
    "name": "Straits Times",
    "slug": "straits-times",
    "url": "https://www.straitstimes.com/singapore/environment/st-explains-psi-or-pm2-5-what-air-quality-measures-should-i-refer-to-during-the-haze"
  },
  "original_language": "en",
  "account": "During the haze on Aug 24, Singapore's Pollutant Standards Index (PSI) in the central region neared unhealthy levels, with a 24-hour PSI reading of 96. Two key air quality measures, the 24-hour PSI and the 1-hour PM2.5 readings, are crucial for planning outdoor activities. During hazy periods, it is the 1-hour PM2.5 reading that indicates current air quality, with values above 56ug/m3 causing elevated concerns. PM2.5 particles are so small they can penetrate deep into the lungs and bloodstream, posing significant health risks. The 24-hour PSI, computed from the past 24 hours, provides a general snapshot of air quality. When the PSI crosses 100, haze is declared, and the National Environment Agency issues a 24-hour PSI forecast to predict air quality for the next 24 hours. For immediate outdoor activities, focus on PM2.5 values. If these readings are between 151ug/m3 and 250ug/m3, avoid strenuous exercise for the next hour. Vulnerable groups like seniors, pregnant women, children, and those with lung or heart disease should minimize all outdoor activities. N95 masks are unnecessary for short-term exposure but are recommended for prolonged outdoor activities when the air quality is hazardous, with a PSI over 300. To manage indoor air, close doors and windows, and use portable air purifiers if necessary. When planning outdoor activities the following day, consult the 24-hour PSI forecast and heed the accompanying health advisories.",
  "summary": "The PSI forecast and the 1-hour PM2.5 readings serve different functions.",
  "key_points": [
    "24-hour PSI reading of 96 neared unhealthy levels on Aug 24",
    "1-hour PM2.5 values above 56ug/m3 indicate elevated air quality concerns",
    "Vulnerable groups should minimize outdoor activities when PSI over 300"
  ],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}