PREVENTING HEAT STRESS In most cases, heat stress can be prevented or, at least, the risk of developing heat stress can be reduced.

A number of engineering controls can help reduce heat exposure. These include:

• general and local exhaust ventilation in areas of high heat
• shielding of radiant heat sources, such as furnaces or hot machinery
• elimination of steam leaks
• use of cooling fans or personal cooling devices, such as cooling vests
• use of power tools to reduce manual labor

Work Practices

• Clothing: Wear loose-fitting, lightweight clothing, such as cotton, to allow sweat to evaporate. Light colors absorb less heat than dark colors. When working outside, wear a lightweight hat with a good brim to keep the sun off your head and face.
  
  
• Drinking: Drink plenty of liquids, especially if your urine is dark yellow, to replace the fluids you lose from sweating – as much as one quart per hour may be necessary. Water and/or sports drinks are recommended. Since caffeine is a diuretic (makes you urinate more), beverage such as cola, iced tea and coffee should be avoided. Thirst is not a reliable sign that your body needs fluids. When doing heavy work, it is better to sip rather than gulp the liquids.
• Work Schedule: If possible, heavy work should be scheduled during the cooler parts of the day. Otherwise, alternate heavy work in the heat with lighter work or work in cooler areas. When the temperature humidity index is between 84 and 93 (Warning Zone), try to minimize the amount of time working in the heat such that approximately half of each hour is spent doing heavy work in the heat. When the temperature humidity index is 94 or higher (Danger Zone), this should be further minimized to approximately one quarter of each hour spent doing heavy work in the extreme heat.
• Acclimatization: New employees and workers returning from an absence of two weeks or more should have 5 days to get used to the heat. Begin with 50 percent of the normal workload and time exposure the first day and gradually build up to 100 percent on the fifth day.
• Body Weighing: Workers may be at greater risk of heat stress if they lose more than 1.5% of their body weight in a single day from sweating.

Personal Protective Equipment

When work must proceed in hot conditions at Princeton, personal cooling systems may help reduce the risk of heat stress. There are several systems available through health and safety catalogs, including the following:

• Heat reflective clothing may alleviate the problem of radiant heat sources, such as furnaces. However, if the worker is fully covered, he or she will have trouble evaporating sweat.
• Ice vests or cooling vests remove heat from the skin. They are relatively inexpensive and allow freedom of movement.
• Liquid cooling systems also remove heat from the skin. Cool liquid flows in the suit around the body and carries the heat away.

Training

Employees and supervisors need to be trained to be able to detect early signs of heat stress. Employees must understand the need to replace fluids and salt from sweat and recognize the signs of dehydration, fainting, heat cramps, heat exhaustion, and heat stroke.
Supervisors should watch for signs of heat stress and allow workers to interrupt their work if they are extremely uncomfortable. Supervisors should also ensure that work schedules allow appropriate rest periods and ensure liquids are available. They should use appropriate engineering controls, personal protective equipment and work practices to reduce the risk of heat stress.