{
  "id": "disaster/n95-mask-not-needed-until-psi-300",
  "signature": "AI tells a healthy person in Singapore to wear an N95 mask outdoors whenever PSI is in the 'Unhealthy' band during haze season",
  "signature_zh": "",
  "regex": "(singapore.*haze.*mask|psi.*singapore.*n95|singapore.*n95.*haze|haze.*singapore.*mask)",
  "domain": "disaster",
  "category": "hazard_misjudgment",
  "subcategory": null,
  "root_cause": "Singapore's official haze health guidance (HealthHub, under the Ministry of Health/Health Promotion Board) sets the N95 mask threshold for healthy individuals at PSI above 300 (the 'Hazardous' band), not the much lower 101-200 'Unhealthy' band. People with chronic heart/lung disease are advised to mask earlier, above PSI 200. Below those thresholds, official guidance is to reduce prolonged or strenuous outdoor exertion, not to mask up. NEA's 24-hour PSI forecast (via haze.gov.sg or the myENV app) is the index the Ministry of Manpower directs employers to monitor for outdoor-work decisions.",
  "root_cause_type": "generic",
  "root_cause_zh": "",
  "versions": [
    {
      "version": "any",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "Tell a healthy person to put on an N95 mask as soon as PSI enters the 'Unhealthy' (101-200) band during Singapore's haze season",
      "why_fails": "HealthHub's official haze advisory sets PSI bands at 0-50 Good, 51-100 Moderate, 101-200 Unhealthy, 201-300 Very Unhealthy, and 300+ Hazardous, and states N95 masks are recommended for healthy individuals only when PSI exceeds 300. In the 101-300 range, the guidance for healthy people is to reduce prolonged or strenuous outdoor physical exertion, not to mask up - over-recommending masks at moderate PSI wastes N95 supply and can give a false sense of continuous need.",
      "fail_rate": 0.6,
      "condition": "Healthy individual, PSI between 101 and 300",
      "sources": [
        "https://www.healthhub.sg/highlights-and-insights/health-safety-advisory/how-to-protect-yourself-against-haze"
      ]
    },
    {
      "action": "Apply the same PSI mask threshold to someone with chronic heart or lung disease, elderly, or pregnant as to a healthy adult",
      "why_fails": "HealthHub's guidance sets a lower N95 threshold of PSI above 200 for people with chronic lung/heart disease, a full band below the 300 threshold for healthy individuals, since these groups are more vulnerable to particulate exposure at lower concentrations.",
      "fail_rate": 0.5,
      "condition": "At-risk individual (chronic lung/heart disease, elderly, pregnant)",
      "sources": [
        "https://www.healthhub.sg/highlights-and-insights/health-safety-advisory/how-to-protect-yourself-against-haze"
      ]
    }
  ],
  "workarounds": [
    {
      "action": "Check the current 24-hr PSI forecast on NEA's haze microsite (haze.gov.sg) or the myENV app before deciding on outdoor activity or masking, rather than assuming a fixed rule of thumb",
      "success_rate": 0.85,
      "how": "MOM directs employers to the same 24-hr PSI forecast plus NEA's health advisories to decide protective measures for outdoor workers, so this is the authoritative index to check first.",
      "condition": "Planning outdoor activity or work during haze season",
      "sources": [
        "https://www.mom.gov.sg/faq/haze/which-haze-index-should-employers-monitor-so-as-to-decide-what-measures-to-take-to-protect-their-workers",
        "https://www.haze.gov.sg/"
      ]
    },
    {
      "action": "For healthy adults, reduce prolonged/strenuous outdoor exertion once PSI passes 100-200 and reserve N95 masks for PSI above 300; for at-risk groups, mask above 200 and consult a doctor for extended outdoor exposure",
      "success_rate": 0.8,
      "how": "",
      "condition": "Deciding when to mask during elevated PSI",
      "sources": [
        "https://www.healthhub.sg/highlights-and-insights/health-safety-advisory/how-to-protect-yourself-against-haze"
      ]
    }
  ],
  "workarounds_zh": [],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": null,
  "official_doc_section": null,
  "error_code": null,
  "verification_tier": "ai_generated",
  "confidence": 0.68,
  "fix_success_rate": 0.75,
  "resolvable": "true",
  "first_seen": "2026-08-30",
  "last_confirmed": "2026-08-30",
  "last_updated": "2026-08-30",
  "evidence_count": 3,
  "tags": [],
  "locale": "en",
  "aliases": [
    "disaster/n95-mask-not-needed-until-psi-300/sg"
  ]
}