Depending on your employee's workload, it only takes an interior building temperature of 70 degrees Fahrenheit or higher to start the process of heat stress. The combination of heat, work exertion, and dehydration are the 3 elements that primarily contribute to heat-related illnesses. But during the summertime, even lighter workloads combined with dangerous heat can cause worker discomfort and overheating. During the summer, heat stress can be a real concern when employees are wearing industrial clothing, personal protective equipment (PPE), or work uniforms.

If this gear is not breathable and able to transfer body moisture from the surface of the skin, they can contribute significantly to employee overheating - especially in the summertime.

Protective Clothing Risks in Extreme Heat

Some protective clothing can be too thick or heavy, effectively trapping hot air between the worker's clothing and body. And when the outfit obstructs air flow, such as fitted arms or leg cuffs, there is no path for hot air to escape or cool air to enter. The worker's uniform acts as an insulator encouraging a micro-climate of hot, humid air and discouraging the evaporation of moisture and the flow of air.

A study entitled Heat Stress Evaluation of Protective Clothing Ensembles discusses two paths of heat transfer through clothing - dry heat transfer and moisture transfer.

Dry Heat Transfer - the exchange of heat between skin and uniform that is driven by the increased environmental temperature and can happen by way of three different thermodynamic phenomena:

  • Conduction - transfer of heat between two solid surfaces in contact and with different temperatures
  • Radiation - Heat transmitted through empty space by thermal radiation (infrared heat or solar heating)
  • Convection - the transfer of heat from one place to another by the physical movement of fluids (sweat and air moisture)

Moisture Transfer - Evaporative heat transfer (or wet heat transfer) occurs when water vapor in the air, which includes both air humidity and the body's evaporating perspiration, is converted into latent heat. Latent heat is similar to the process of boiling water evaporating until it has all been converted into vapor and produces steam heat. Likewise, the body's water content or perspiration will generate heat by way of moisture evaporating at a high temperature.

When protective clothing traps air and moisture, workers will experience evaporative heat gain and multiple forms of dry heat transfer between clothing, skin, and the environment. When that environment is hot or it is a hot summer day, the worker will experience more heat gain instead of heat loss which is the normal mechanism that sweating provides to cool the body. As part of a safe and healthy work environment during the summer, breathable uniforms should be used whenever possible to minimize heat gain for workers whose jobs may also expose them to high environmental temperatures.

The Role of Ventilation in Dry and Wet Heat Transfer

Except for heat radiating from the sun or standing near an extremely hot surface, the other forms of wet or dry heat transfer can be significantly reduced with ventilation built into the worker's uniform. When protective clothing is breathable, the insulating properties of the uniform fabric is reduced. Less insulation means a greater rate of air exchange. When air movement through holes and openings in the fabric of protective clothing is accelerated it can prevent steam build-up and moisture heat transfer due to the evaporation of water droplets. 

The definition of ventilation when applied to PPE or work uniforms is as follows:

Protective Clothing Ventilation - is rated on a scale that measures the amount of heat transferred directly from the skin to the air through vents and openings in the clothing. The amount of PPE ventilation will depend on environmental temperatures, skin moisture levels, features built into the clothing, the type of fabric, and the activities being performed. 

Breathable clothing with excellent ventilation will reduce convection dry heating by providing exit routes for convected heat to escape. Conducted heat is reduced when uniforms do not fit tightly and eliminates as many points of skin contact with the fabric as possible. While radiant heat near hot equipment cannot be eliminated, workers will definitely feel cooler when the clothing reduces steam build-up and allows air flow between the fibers of the material.

Any work process or job where the worker is exposed to higher temperatures than they are normally accustomed to can benefit from breathable uniforms that allow for increased ventilation. Industrial locations, outdoor operations, working near radian heat sources, processes that generate high humidity, or jobs that require strenuous physical activity all have the potential to induce heat stress in workers.

Additional Factors for Summer Heat Stress

Employers cannot account for all the factors that can contribute to a worker that has a reduced tolerance to heat. Here are some additional factors that can contribute to illnesses in certain individuals while working in the summer heat:

  • Employees that have used alcohol or drugs
  • Drinking caffeine or those taking certain medications
  • Overweight workers or those that lack good physical fitness 
  • A person's metabolism rates or other medical conditions
  • Those who does not drink enough water or moderate their activities
  • Employees who have not been properly acclimatized for hot working conditions

Workers that are heat intolerant will likely experience heat stress symptoms faster. These include weakness, dizziness, headaches, and in extreme cases - cramping and nausea. When heat stress is left untreated, it can lead to a heat stroke. For these reasons, it is essential that employers provide a comfortable work environment, fans for immediate cooling, and access to plenty of cold drinking water.

Providing areas with a lower environmental temperature, accelerating the employee's ability to self-ventilate with fans, and replacing the body's lost water reserves will also apply to workers that struggle with heat intolerance.

How to Minimize Occupational Heat Stress

There are obvious work environments or activities that will expose workers to heat stress. But some are not so obvious, where worker's body temperatures may rise due to overexertion in combination with the warmer summer weather. These are instances where a workplace summer safety programs should encourage safe work habits during hot weather, including:

  • Have access to a cool room with fans where workers can recover and reduce their deep core temperature
  • Train employees to recognize the symptoms of heat stress so that they can get medical help before it escalates
  • When suffering from heat stress, employees should take off protective garments immediately
  • Wear breathable protective garments designed to provide workers with as much ventilation as possible

For outdoor workers, always having plenty of bottled water to drink along with a water source to pour over the body can replenish moisture loss through the skin. Workers should also wear sunscreen, take plenty of breaks, and wear uniforms that are breathable or when uniforms are not mandatory, encouraged to wear cotton clothing during the summer.

Cotton tee-shirts and socks along with Chambray or denim fabric slacks provide a lightweight and breathable solution for non-uniformed employees. Cotton will also absorb body sweat and provides good ventilation which will allow body heat to escape making the worker feel cooler. For jobs that require workers to be uniformed, consider the Body Filter 95+ manufactured by International Enviroguard. 

Body Filter 95+ protective clothing features a roomy, seamless shoulder area  and a wider, gusseted crotch to facilitate air flow and gives your workers more room for added comfort. The breathable fabric will help keep workers cooler and can assist in avoiding heat stress. 

The material resists tears and they are disposable to reduce contamination in food, beverage, or other processes. For environments where particulate contamination is a concern, these disposable PPE garments will filter out 95%-99% of 0.3 micron particles—similar to an N95 respirator. Visit International Enviroguard online for a wide selection of personal protection equipment that will benefit your workers during the hot months of summer.