About the Heat Stroke and Heat Index (WBGT)

The Central Meteorological Observatory has issued high temperature warnings for 9 consecutive days. The high temperature in the south will continue until the 17th.

(Excerpt from China Meteorological Network)
High temperatures have continued recently, and red high temperature warnings have been issued in many placesHeat stroke incidents frequently occur under continuous high temperatures: many people in Zhejiang Province were diagnosed with heat stroke, a renovation worker in Nanjing suffered from heat stroke, and Sichuan West China Hospital admitted 3 cases of heat stroke in one day

Heat stroke and heat index (WBGT)

1. Definition of heat stroke 
Heat stroke is a general term for disorders that occur in hot summer environments. It can be divided into heat fainting, heat cramps, heat fatigue, heat stroke, etc.
An acute disease with central nervous system and/or cardiovascular dysfunction as the main manifestation caused by dysfunction of the body temperature regulation center, sweat gland failure and excessive loss of water and electrolytes in the hot summer season, high temperature and/or high humidity environment. According to clinical manifestations, heat stroke can be divided into pre-heatstroke, mild heatstroke and severe heatstroke. Among them, severe heatstroke is further divided into heat cramps, heat exhaustion and heat stroke. Among them, the most serious is heat stroke, which can lead to death.

2. Heat Index (WBGT Index)

The WBGT index can reflect the impact of temperature and humidity on people. It covers three small indicators: temperature, humidity, and radiant heat (sometimes, wind speed is also taken into account to improve accuracy). The basic calculation method is: WBGT = (0.7×Tw) + (0.2×Tg) + (0.1×Ta).

Among them, Tw, Tg, and Ta represent the wet bulb temperature, black bulb temperature, and dry bulb temperature respectively.

If indoors, or where solar radiation can be neglected, use the following method: WBGT = (0.7×Tw) + (0.3×Tg).

Work in hot environment refers to work under abnormal working conditions with high temperature, strong heat radiation, or high humidity (relative humidity ≥ 80%RH), and the wet bulb globe temperature index (WBGT index) exceeds the prescribed limit. It includes work in hot weather and work in the workplace.

The probability of heat damage increases significantly with the increase of WBGT temperature during high temperature work.

(Table from OSHA)

3. Thermal Index (WBGT) Measurement

Instrument: Wet Bulb Globe Temperature (WBGT) Index

JT2011 Wet Bulb Globe Temperature (WBGT) Index Meter

4. Limits on the time allowed for continuous exposure to heat during high temperature work

According to my country's current standards (GB/T4200-2008), the duration of high-temperature work is as follows: see the table below, and the rest period must not be less than 15 minutes.

5. Diagnostic criteria for occupational heat stroke

1. Diagnostic principles

Based on the occupational history of workers working in high temperatures (mainly referring to the meteorological conditions during work) and main clinical manifestations such as fever, muscle cramps or syncope, and excluding other similar diseases, occupational heat stroke can be diagnosed.

2. Symptoms of heat stroke

The precursors of heat stroke (observation objects) refer to the symptoms such as dizziness, headache, thirst, sweating, general fatigue, palpitations, inattention, and uncoordinated movements that occur after working in a high-temperature workplace for a certain period of time, with normal or slightly elevated body temperature.

3. Diagnosis and grading criteria

(1) Mild heat stroke
In addition to the worsening of the symptoms that preceded heatstroke, mild heatstroke also presents symptoms such as flushed face, heavy sweating, rapid pulse, and a body temperature rising to above 38.5℃.

(2) Severe heat stroke
Severe heat stroke can be divided into three types: heat stroke, heat cramps and heat exhaustion. Mixed types can also occur.

(3) Heat stroke
Heatstroke (including sunstroke) is also known as heatstroke-related fever. It is characterized by sudden onset of the disease in a high temperature environment, with body temperature reaching over 40°C. In the early stages of the disease, there is heavy sweating, followed by "no sweating", which may be accompanied by dry and hot skin and varying degrees of impaired consciousness.

(4) Heat cramps
Heat cramps are mainly manifested by obvious muscle cramps accompanied by contraction pain. They are more likely to occur in the limb muscles and abdominal muscles that are more active, especially the gastrocnemius muscles. They are often symmetrical. They come and go. The patient is conscious and his body temperature is generally normal.

(5) Heat exhaustion
The onset is rapid, and the main clinical manifestations are dizziness, headache, sweating, thirst, nausea, and vomiting, followed by cold and wet skin, decreased blood pressure, heart rhythm disorders, mild dehydration, and slightly high or normal body temperature.

6. On-site measurement of high temperature working environment

1. Set up the tripod at the measuring point and fix the WBGT indexer on the tripod

2. Data processing and analysis through software

3. Remotely view data via 4G network (optional wireless function)

4. Outdoor and high temperature workshop WBGT sound and light warning device (customized product)

LED lights and sound alarms provide timely high temperature warnings to on-site workers, allowing them to evacuate the site quickly to avoid heat injuries such as heat stroke.

7. Protective measures for high temperature work

1. Improve working conditions, equip with protective facilities and equipment, and strengthen ventilation equipment and heat dissipation in production sites.

2. Strengthen personal protection, avoid high temperature working environment, stay away from high heat sources as much as possible, and avoid or reduce heat radiation;

3. Develop a reasonable labor rest system, reduce work during high temperature periods, increase the number of breaks, avoid outdoor high temperature work during high temperature periods as much as possible, and provide employees with a cool resting place

4. There should be enough clean drinking water, and supply of cool drinks, cooling products and nutritional supplements to prevent heatstroke. It is best to drink small amounts of water multiple times. At the same time, be careful not to wait until you are thirsty to drink water.

5. Prepare towels, wind oil, Huoxiang Zhengqi water, Rendan and other heat-prevention and cooling products. Develop a reasonable diet system and supplement protein and calories in the diet.

6. If the operator has any contraindications to high temperature, they should report it in time. The team leader should not arrange the employees with contraindications to high temperature to work in high temperature.

7. Pay attention to the hot weather warnings issued by the weather forecast

8. First aid measures for heat stroke

1. Place the patient in a cool place, lie flat, and loosen tight clothing.

2. Wipe your body with a wet towel and use a fan to quickly lower the ambient temperature.

3. Drink some light salt water; those who are sober can also drink a little Ren Dan, mung bean soup, etc.

4. The unconscious person should be sent to the hospital immediately.