Fans, misters and air conditioning units are engineering controls that can be used to cool workers and reduce heat stress and the incidence of heat-related illnesses.

MovinCool Climate Pro X14

 

An example of a portable Air Conditioning Unit (Photo courtesy of MovinCool)

Cooling Capacity Rating Conditions: 95°F at 60% Relative humidity; 13,200 Btu/h
Operating Conditions (Minimum - Maximum):  at 50% Relative Humidity from 70° - 113°F
Dimensions (inches):  22W x 29D x 48H
Weight (pounds): 165

Studies have documented the impact of heat-related illnesses on productivity. According to California’s largest provider of workers compensation insurance, “[r]ecognizing the warning signs and symptoms of heat-related illnesses and using preventive and control measures can reduce the frequency and severity of heat illness while increasing worker productivity (Preventing Heat Related Illnesses).’

Engineering controls are preferred over administrative controls and personal protective equipment but a combination of controls may be necessary.

Implementing a comprehensive heat stress program can have a positive impact on safety and productivity. Ensuring adequate hydration, rest and cooling methods helps to maintain lower risks for heat stress and other heat-related issues.

For very high heat conditions, such as work in impervious protective suits, cooling vests using ice or chilled water may reduce body core temperatures. Where supplied breathing air is provided, cyclones or other devices are available which chill the breathing air or air for positive pressure protective clothing.

Employers should provide training to workers so they understand what heat stress is, how it affects their health and safety, and how it can be limited.

Heat stress is often accompanied by exposure to sunlight and the ultraviolet radiation that is a part of sunlight. Ultraviolet radiation can damage skins cells and increase the risk for skin cancer. Employers should train workers on the risks and prevention of exposure to ultraviolet radiation and provide shaded work and rest areas. Workers should take breaks in the shade and wear sunscreen and protective clothing.

Heat stress can also lead to kidney diseases. A 2011 study of 37,816 Thai workers examined the relationship between occupational heat stress and kidney disease. After analyzing data from both 2005 and 2009, the study found that men exposed to extended periods of heat stress were 2.22 times more likely to develop kidney disease than those who did not experience such conditions. In addition, men 35 years old and older experienced a 2.2% chance of developing kidney disease when exposed to heat stress while those not exposed experienced a 0.4% chance (Tawatsupa, 2012).

Although it is universally recognized that maintaining adequate levels of hydration to prevent heat stress is important, many workers and supervisors ignore the facts and the signs of dehydration. Strategies to help promote good hydration are often neglected. Recent studies have shown a consistent pattern of poor hydration in workers employed in industries where environmental heat stress is a common problem. An Australian research study, for example, tested workers by administering a urine test during working hours. The results showed that greater than 70% of the 710 workers in the study showed signs of poor hydration, and 51% showed hydration poor enough to put the workers at high risk for heat related illnesses (Miller, 2009).

The American Conference of Governmental Industrial Hygienists (ACGIH) assigned heat a Threshold Limit Value (TLV) based on time-weighted averages (TWA) of Wet-Bulb Globe Temperature (WBGT). WBGTs are not the same as standard temperature readings because they integrate the effect of humidity through a wet bulb reading and radiant heat with a black globe reading. The TLVs are ratios of work to rest needed for different WBGT values. For example, within every hour worked in the cycle, the percentage of time to work during that hour at temperatures at or above the TLV is shown in the first column. WBGT values must be adjusted for the type of clothing worn (ACGIH, 2012). The TLV booklet goes into great detail about heat stress prevention, measurement and control. It can be purchased at: http://www.acgih.org/store/.

₁ Sitting with light manual work with hands or hands and arms, and driving. Standing with some light arms work and occasional walking.
₂ Sustained moderate hand and arm work, moderate arm and leg work, moderate arms and trunk work, or light pushing and pulling. Normal walking.
₃ Intense arm and trunk work, carrying, shoveling, manual sawing; pushing and pulling heavy loads; and walking at a fast pace.
₄ Very intense activity at fast to maximum pace.

Andrew Kingston, Michael R. Cooper and Bruce Lippy - The Lippy Group

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