Heat Stress | MillerWelds


Heat Stress Protection

Heat stress is not only a serious condition for workers, but it can greatly reduce productivity and increase operator errors. The heat of the welding arc and added warmth of protective clothing can make already hot conditions even more intense for welders. Miller cooling products help lower body temperatures and can be an effective solution to help improve the welder's well being and performance on the job.

Statistics & Trends: Heat Stress


Nonfatal occupational injuries and illnesses involving days away from work in a single year due to exposure to environmental heat. 


The number of people that died in the U.S. from exposure to excessive heat in 2017.

98º F

The ideal body temperature for a human body to function at optimal performance.


The percentage a worker’s output can decrease for every degree above 80º

The Talk: Terms & Definitions

Acclimatization: The time needed for physiological adaptation to extreme temperature changes. An average individual takes about 1 to 2 weeks to adapt to extreme hot temperatures.

Body Heat Balance: Steady state equilibrium between body heat production and heat loss to the environment.

Wet Bulb Globe Temperature (WBGT): Composite temperature used to estimate the effect of temperature, humidity, wind speed, and radiation (usually sunlight) on humans. Used by industrial hygienists to determine appropriate exposure levels to high temperatures. It can also be adjusted and measured for indoor indexes. 

Wet Bulb (WB): The temperature at which water evaporates into the air. It is significant when compared to skin temperature because of the affect it has on how much of a worker’s sweat evaporates.

Threshold Limit Values (TLV): Guidelines designed for use by industrial hygienists in making decisions regarding safe levels of exposure to various chemical substances and physical agents found in the workplace.

Types of Heat Stress

Heat Stroke: Critical condition – Call 911! Occurs when the body can no longer control its own temperature due to failure of the sweating mechanism, causing body temperature to rapidly rise. Heat Stroke can cause permanent disability or death.

Heat Cramps: Sweating depletes the body’s salt and moisture levels, causing painful cramps.

Heat Collapse (Syncope): Dehydration and lack of acclimatization can contribute to fainting or dizziness. This condition can be very serious if workers are operating machinery.

Heat Rash: Skin irritation (typically a cluster of small red blisters) caused by excessive sweating during hot, humid conditions that gives a prickling sensation.

Heat Fatigue: Typically occurs due to lack of acclimatization, leaving the worker tired and with impaired performance.

There are many different ways to measure and determine if an environment is too hot for workers. Two of the more common
means are the Heat Index and Permissible Heat Exposure TLV, providing information on when caution needs to be taken and
recommended work/rest regimens.

Permissible Heat Exposure Threshold Limit Value (TLV)

Heat Index  Risk Level Protective Measures
Less than 91° Lower (Caution) Basic heat safety and planning
91°F to 103°F Moderate Implement precautions and heighten awareness
103°F to 115°F High Additional precautions to protect workers
Greater than 115°F Very High to Extreme Triggers even more aggressive protective measures

These TLV levels are based on the assumption that nearly all acclimatized, fully clothed workers with adequate water and salt
intake should be able to function effectively under the given working conditions without exceeding a deep body temperature
of 100.4°F. They apply to physically fit and acclimatized individuals wearing light summer clothing.