With the summer months quickly approaching, that variable threat called “heat stress” is on the program planner of most safety pros. In order to combat this potentially deadly hazard, it is important to understand the various levels of heat stress, the appropriate steps for recovery, as well as the controls and personal protective equipment (PPE) you can utilize in planning your heat stress protection program.

A wide range of industries — and a long list of conditions — are conducive to heat stress related disorders. The most common workplace conditions include air temperature, humidity level, radiant heat, direct physical contact with hot objects and physical exertion. In addition, those activities that require employees to wear semi-permeable or non-permeable protective clothing tend to lead to additional heat stress risk.

Difficult to manage
Heat stress can be a difficult threat to manage, as environmental and individual variables combine, leading to numerous causal factors. The best protection plans call for standard environmental controls while being aware of those causal variables that will uniquely affect each individual employee. Environmental variables include air temperature, radiant heat and air velocity. Individual variables include age, weight, physical fitness, metabolism, use of alcohol and/or drugs, medical conditions and prior heat injury.

Let’s take a look at the three major forms of heat-related illness and their related recovery strategies:

Heat cramps: Heat cramps are muscle spasms usually affecting the arms, legs or stomach. These painful cramps generally occur several hours after the heat exposure while the body is at rest. Heat cramps are caused by the excessive loss of bodily fluids, i.e. heavy sweating.

Replenishing the body with water alone does not restore the depletion of salt and potassium, causing the muscles to react. Although heat cramps typically don’t cause permanent damage, they are painful enough to result in lost time and workplace disruption.

Recovery: An individual suffering from heat cramps will need to replenish the body’s fluids and minerals. Electrolyte fluids such as Gatorade and foods rich in potassium such as bananas will help restore balance.

Heat exhaustion: Heat exhaustion is more serious than heat cramps. Prolonged exposure to heat in combination with physical exertion can overwork the body’s internal “air conditioning” system. In heat exhaustion, blood vessels and capillaries, which enlarge to cool the blood, collapse from loss of body fluids and necessary minerals. Bodily fluids are not being adequately replaced.

The symptoms of heat exhaustion include headache, heavy sweating, intense thirst, loss of coordination, nausea, fatigue, dizziness, loss of appetite, impaired judgment, hyperventilation, tingling of the extremities, anxiety, cool moist skin, weak pulse and low pulse.

Recovery: A person suffering from heat exhaustion should be moved to a cool location such as a shaded area or air-conditioned building. They should lie down with their feet slightly elevated, have their clothing loosened, have cool, wet cloths put on them, and be put near a fan. Bodily fluids should be replenished followed by a period of at least 24 hours rest. A return to strenuous activities should be gradual and carefully monitored.

Heat stroke: The most serious of heat stress related illness, heat stroke can often result in permanent disability and even death. Heat stroke occurs when the body is completely depleted of its water and salt supply. The body reacts by raising the internal temperature to critical levels. The symptoms of heat stroke include a high body temperature, lack of sweating, irrational behavior, confusion, loss of consciousness and convulsions.

Recovery: A person suffering from heat stroke will require immediate emergency medical attention to survive. It is imperative to get the body temperature reduced within seconds by moving the individual to a cool location, removing all outer clothing, applying water or wet cloths and even cold packs while fanning them until emergency personnel arrive.

Reduce exposure
There are a number of strategies employers can take to guard against heat stress related injury and illness. Recommended controls to reduce heat stress exposure and liability include the following:

• Conduct workplace assessments regularly to ensure that engineering controls such as air conditioning, fans, ventilation systems and shielding devices are working properly.
• Perform environmental monitoring (i.e. temperature and humidity readings) to identify potential risks. Indoor/outdoor portable heat stress monitors identify how long an individual can safely work in any environment. The use of a “wet bulb globe” thermometer is recommended to measure ambient humidity, which is directly linked to heat stress.
• Conduct a job analysis to determine how to reduce physical exertion through the assistance of power tools and equipment.
• Utilize an acclimatization program whereby workers are exposed to heat stress for progressively longer periods of time. This allows the body to adapt, reducing the threat of heat stress.
• Provide water and electrolyte fluids to assist in reducing heat stress related illness and injury.
• Provide medical screening designed to assess an individual’s ability to tolerate heat stress.
• Offer ongoing training programs designed to educate employees on identifying symptoms, treatments and personal responsibility when dealing with heat stress.
• Implement “worker monitoring” programs to ensure that exposed workers are wearing appropriate PPE, taking regular breaks and restoring bodily fluids.
• Utilize job rotation and use of shift work to limit the extent and length of the exposure.

Personal protection
Once you’ve implemented the proper controls to reduce heat stress exposure, make sure your workers are wearing appropriate personal protection. Some examples of PPE aimed at reducing heat stress illness and injury include the following:

Reflective clothing. This includes aprons, jackets and full-body suits that protect from the absorption of radiant heat. Although this type of PPE reduces the absorption rate, it can also reduce the amount of air exchange needed to cool the body; therefore it is important to determine if this type of protection is appropriate for the circumstance.

Ice vests. There are many styles and types of ice vests available. Most accommodate ice or carbon dioxide packs. They offer maximum mobility and cooling protection but can be cumbersome and need to be maintained throughout the work shift.

Wetted clothing. Using terry cloth or cotton suits that are soaked in water can be effective in high temperatures and low humidity.

Water cooling garments. There are many types of devices designed to cool parts of the body. Each works using ice or cooled water and has its own set of advantages and disadvantages based on the work environment and the user.

Respirator use - SCBA (self-contained breathing apparatus). Where respirators are necessary, these devices offer constant cool air circulation. They can be lightweight, comfortable and have recently become more affordable.

The most successful heat stress protection programs will use a thorough combination of employee screening, training, internal controls and PPE — along with a good, healthy dose of common sense.

SIDEBAR: Work practices to prevent or reduce heat stress

• Training program
• Liquid replacement program
• Acclimatization program
• Work/rest schedule
• Scheduling of work during cooler parts of shift
• Cool rest areas (including shelter at outdoor work sites)
• Heat monitoring program
• Proper personal protective equipment
• Circulating air systems
• First-aid program
• Trained personnel
• Provision for rapid cool-down
• Procedures for getting medical attention
• Transportation to medical facilities
• Medical screening and surveillance program