Index WBGT (Wet-Bulb Globe Temperature), or wet bulb temperature, is a composite index widely used for evaluation thermal stress level Heat stress is what humans endure in hot environments. It differs from normal air temperature because it takes into account many other environmental factors.

The factors taken into account in WBGT are a comprehensive measure that incorporates four key factors affecting the human body's thermoregulation: 

• Air temperature (Dry-bulb temperature – Tdcap T sub dTd): Actual ambient temperature.
• Humidity (Natural wet-bulb temperature – Twcap T sub w𝑇𝑤): It affects the body's ability to evaporate sweat and cool itself. The higher the humidity, the harder it is for sweat to evaporate, and the harder it is for the body to cool down.
• Thermal radiation (Black globe temperature – Tgcap T sub gTg): The amount of heat the body absorbs from sunlight or other heat sources (such as asphalt surfaces, walls, furnaces).
• Air movement speed: Wind helps to increase the evaporation of sweat, keeping the body cooler.

Heat stroke index meter with black ball / Heat stroke index monitor A&D AD-5698B

Meaning and applications

WBGT It is used by organizations such as OSHA (U.S. Occupational Safety and Health Administration), the military, and sporting events as a guideline to determine safe levels for working or performing physical activity in high temperatures. 

• Purpose: Helps prevent heat-related illnesses such as heatstroke and sunstroke.
• Safety instructions: Based on WBGT values, organizations make recommendations on work/rest times, exercise levels, and hydration needs to protect human health. 

For example, when the WBGT index is high (e.g., above 31°C), strenuous physical activity is usually prohibited or severely restricted to avoid danger.

Sato 8312-00 Heatstroke Heat Index Meter SK-170GT ( temperature: 0.0 to 50.0°C/ Black globe temperature:0.0 to 80.0°C/ WBGT index: 0.0 to 50.0°C / Humidity:10.0 to 95.0%rh)

The importance of the WBGT index:

WBGT is important because it provides a realistic and reliable assessment of heatstroke risk, superior to other indicators such as the Heat Index (which only considers temperature and humidity in the shade). The appropriate WBGT (Wet Bulb Globe Temperature) depends on each individual's level of physical activity and thermal acclimatization. A WBGT below 25°C (77°F) It is generally considered safe for most people and activities.

General guidelines on WBGT safety levels

Recommendations for the workplace in Vietnam

According to national technical standards on workplace microclimate in Vietnam, permissible exposure limits vary depending on the intensity of work: 

• Light labor: The WBGT limit is approximately 30°C.
• Heavy labor: The WBGT limit is approximately 25°C.

When the WBGT index reaches 32°C For strenuous work, workers should be given a minimum 10-minute break every hour in a cool place, and the break time should be longer when this figure is higher.

• Accurately assess heat stress: WBGT is an international standard (recognized by ISO and ACGIH) for assessing the level of heat stress on the bodies of workers and athletes. It shows the “true sensation of heat” caused by all environmental factors.
• Preventing heat-related illnesses: Organizations such as OSHA (the U.S. Occupational Safety and Health Administration), the military, and sports federations use specific WBGT thresholds to implement preventative measures.
• Workplace and sports safety guidelines: Based on the WBGT index, guidelines are established to regulate operations, including:
  • Work/rest ratio: Reduce working hours and increase rest time when WBGT is high.
  • Regulations regarding rehydration: Ensure workers/athletes drink enough water.
  • Restricted activities: Limit or cancel high-intensity training/competition sessions when temperatures are dangerously high.

A&D AD-5696 (0～50℃/20%RH～90%RH)

Semiki is a official and reputable distributor We specialize in measuring instruments and auxiliary equipment in the Vietnamese market, with particular experience collaborating with equipment manufacturers from Japan and other international brands. 

Reasons why you can trust Semiki:

• Authorized distributor: Semiki presents itself as the official distributor of many well-known measuring equipment brands, such as IMADA, Fluke, Sato Keiryoki, KEM, etc., in Vietnam. This ensures the clear origin of the products, guaranteeing they are not counterfeit or of poor quality.
• Experienced and qualified: The company has been operating in the field of measuring equipment for many years, with a team of engineers and R&D professionals to provide solutions, not just simply sell products.
• Warranty service provided: Semiki provides warranty, maintenance, repair, and calibration services (with optional calibration certificates) for sold equipment. This is crucial for high-precision measuring devices such as WBGT.
• Diverse product range: They offer a wide range of WBGT equipment from reputable manufacturers such as A&D (AD-5690) or models compliant with Japanese industrial standards (JIS B 7922 Class 1.5 or Class 2) from other brands, ensuring you have many options to suit your needs and budget.

Contact Semiki directly: You can find Semiki's contact information (via website or phone number) to request a quote and specific advice.

• Business email: [email protected]
• Phone number (Hotline): +84 979 761 016.
• Website: You can find out more details and send a consultation request via Semiki.com.