The WBGT (Wet Bulb Globe Temperature) meter integrates ambient temperature, humidity, and radiant heat to display the actual thermal stress experienced by the human body. Unlike a simple thermometer, WBGT directly reflects the real risk of heat stroke and heat exhaustion, which is why Korea's Ministry of Employment and Labor strongly recommends WBGT meters at outdoor worksites and high-temperature industrial facilities.
⚠️ As of 2024
According to Korea's Ministry of Employment and Labor, an average of 500+ heat illness occupational accidents are reported annually (2019–2023), with fatalities recorded every year. WBGT ≥33°C is the recommended threshold for work suspension.
(Source: Ministry of Employment and Labor Industrial Accident Status Analysis, 2024)
What Is WBGT?
WBGT was developed by the U.S. military in the 1950s to prevent heat illness among trainees and is now adopted as ISO 7243 international standard. Unlike simple air temperature, WBGT combines three key factors:
| Component | What It Measures | Weighting |
|---|---|---|
| Natural Wet Bulb (NWB) | Humidity & wind effect (sweat evaporation efficiency) | 70% |
| Globe Temperature (GT) | Solar & radiant heat | 20% |
| Dry Bulb (DB) | Actual air temperature | 10% |
WBGT Thresholds & Work Guidelines
| WBGT (°C) | Work Intensity | Recommended Action | Risk Level |
|---|---|---|---|
| Below 27°C | Light / moderate | Normal work permitted | ✅ Safe |
| 27–30°C | Light work | Regular rest breaks + hydration | ⚠️ Caution |
| 30–33°C | Moderate+ work | Min. 15-min rest per hour in shade | 🟠 Warning |
| 33°C+ | All work types | Work suspension recommended · Emergency cooling | 🔴 Danger |
Source: KOSHA GUIDE W-6-2023 "Guidelines for Protecting Workers in High-Temperature Environments", ISO 7243:2017
Heat Illness Types & Symptoms
| Condition | Key Symptoms | First Aid | Severity |
|---|---|---|---|
| Heat Cramps | Muscle cramps, excessive sweating | Move to shade, electrolyte replenishment | ⚠️ Mild |
| Heat Exhaustion | Headache, dizziness, nausea, pale skin | Immediate cooling, IV fluids | 🟠 Moderate |
| Heat Stroke | Loss of consciousness, body temp >40°C, no sweating | Call 119 immediately, full-body cooling (ice packs) | 💀 Life-threatening |
Source: KDCA Heat Illness Emergency Room Surveillance System / KOSHA Heat Illness Prevention Guide
Why a Simple Thermometer Is Not Enough
| Feature | Standard Thermometer | WBGT Meter |
|---|---|---|
| Measures | Air temp only | Temp + humidity + radiant heat |
| Reflects actual body heat load | ❌ No | ✅ Yes |
| Work suspension basis | Subjective | Objective WBGT threshold |
| Legal compliance | ❌ | ✅ ISO 7243 · KOSHA compliant |
| Serious Accident Act defense | Weak | Objective documented evidence |
5-Step Heat Illness Prevention Protocol
- 1Measure WBGT before work: Measure every 1–2 hours between 10 AM–4 PM; log all readings
- 2Enforce WBGT thresholds: Suspend work above 33°C; move workers to shade or air-conditioned areas
- 3Hydrate regularly: 150–200 mL water every 20–30 minutes, with electrolyte supplements
- 4Buddy system: Work in pairs; call 119 immediately if symptoms appear
- 5Retain measurement records: Data logs serve as legal compliance evidence under Korea's Serious Accident Punishment Act
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