Solution Summary: Cooling Clothing and Personal Protective Equipment
Vests, bandanas, hats and other personal protective equipment that reduce heat stress can reduce the risk of heat-related illness.
Description:
Working in high temperatures and high humidity for an extended period can result in heat-related illnesses. Cooling vests, bandanas, hats and other personal protective equipment that reduce heat stress are available and can reduce the risk of heat-related illness.
Cooling vests are designed to maintain comfortable body temperature in high heat and humidity. Weighing 5 pounds or less, cooling vests come in various sizes and have adjustable straps to ensure a comfortable fit. Most products are made from nylon mesh filled with gel material that, once cooled, can be maintained between 59° and 65° F for between 2.5 and 10 hours.
Cooling vests are cooled by submerging them in ice water for 1 to 20 minutes. Alternatively, some vests may be cooled by placing them a refrigerator or freezer until the desired temperature is reached. The vests will not drop below approximately 59° F and therefore do not risk tissue damage, discomfort, or frostbite. When the vest has warmed up, ice water, a refrigerator, or a freezer are used to cool it down for reuse.
Arctic Heat USA Cooling Vest
(Photo courtesy of Arctic Heat USA)
(Photo courtesy of Arctic Heat USA)
- Weight: from 2.2 pounds (size XS to 5XL)
- Cooling Method: cooling crystal/gel packs
- Cooling Time: up to 2 hours
- Recharge Time: 1-3 minutes in ice water for up to 30 minutes cooling; frozen for up to 2 hours
Arctic Heat USA Neck Tie
(Photo courtesy of Arctic Heat USA)
- Cooling part of tube in length: 20 inches; 6 inches on each end of tying
- Cooling Method: cooling crystal/gel packs
- Cooling Time: up to 2 hours
- Recharge Time: 1-3 minutes in ice water for up to 30 minutes cooling; frozen for up to 2 hours
Arctic Heat USA Neck Wrap
(Photo courtesy of Arctic Heat USA)
- Neck wrap dimensions: 15 inches in length by 7.5 inches in width
- Cooling Method: cooling crystal/gel packs
- Cooling Time: up to 2 hours
- Recharge Time: 1-3 minutes in ice water for up to 30 minutes cooling; frozen for up to 2 hours
First Line Technology PhaseCore Cooling Vest
(Photo courtesy of First Line Technology)
- Weight: 3.6 to 5 pounds
- Cooling Method: phase change material - heat-activated cooling
- Cooling Time: 3 to 4 hours depending on style of vest
- Recharge Time: 11 minutes in ice water to 85 minutes in air conditioning - no refrigeration or pre-freezing necessary
- Features: vests are USA-made and range from ANSI 2 compliant hi-viz vests to CarbonX (FR) materials
- One-size fits all universal sizing
Glacier Original Cool Vest - High Visibility with Nontoxic Cooling Packs
Original cool vest with reflective material. (Photo courtesy of Glacier Tek)
- Weight: 5 pounds
- Cooling Method: cooling packs
- Cooling Time: 2.5 hours in 100oF heat
- Recharge Time: 30 minutes in ice water
Glacier Tek Flex Vest - High Visibility with Cooling Packs
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Flex vest with reflective material. (Photo courtesy of Glacier Tek)
- Weight: 5 pounds
- Cooling Method: cooling packs
- Cooling Time: 2.5 hours in 90oF heat
- Recharge Time: 30 minutes in ice water
Risks Addressed:
Heat-related illnesses are caused by working in high temperatures, high humidity and/or direct sun for an extended period of time. Thousands of outdoor workers suffer from heat-related illnesses each year. In addition, many workers die from heat induced illnesses each year. In 2010 alone, 30 workers died from heat stroke.
In hot environments, the body releases excess heat to maintain a stable internal temperature by circulating blood to the skin and through sweating. If the body cannot get rid of excess heat, it will store it and the body's core temperature rises and the heart rate increases. When the body continues to store heat, the person begins to lose concentration and has difficulty focusing on a task, may become irritable or sick, and often loses the desire to drink water. Then, fainting, and even death, can occur if the person does not cool down (OSHA Fact Sheet).
Heat stress can lead to many different conditions, including, but not limited to, heat stroke, heat exhaustion, heat syncope, heat cramps, and/or heat rash. Prevention of heat stress in workers is important (CDC Heat Stress).
How Risks are Reduced:
Cooling vests provide a cool layer close to the skin that readily absorbs body heat, keeping body temperatures in a safe range. Lower body temperatures lead to less water and electrolyte loss via sweating. Overall, cooling vests can maintain safe body temperatures, which decreases the risk of heat illness.
In 1988, the NAVY conducted a study of cooling vests including one that uses frozen gel packs. This vest was tested through several parameters including: rectal and skin temperature, heart rate, oxygen uptake and sweat rate. During work activities in hot environments, the vest proved to keep all parameters at statistically significant lower thresholds than the controls. However, the vests only maintained their integrity for approximately two hours before needing to replace the gel packs with new frozen ones (Pimental, 1992).
A research study completed in 2008 tested the effects of multiple personal cooling equipment devices on the alleviation of heat strain in high temperature work areas. There were eight testing conditions: the control (wearing no cooling products), neck cooling scarf “A”, neck cooling scarf “B”, frozen gel-pack brimmed hat, cooling vest and various combinations of these items. Results showed that rectal temperature was effectively maintained and overall skin temperature and heart rate became more stable when participants wore personal cooling equipment. Researchers concluded that the combination of the cooling vest, a cooling scarf, and the brimmed gel-pack cooling hat showed a considerable amount of heat stress elimination, with a total cooling area of 4.2% of the body surface area, compared to only 3.3% when just a vest was worn (Choi, 2008).
A more recent study indicated that cooling collars alone could actually increase the risk. Researchers tested the hypothesis that cooling the neck region improves exercise ability while working in hot environments. Athletes participating in the study completed four running tests inside an environmental chamber. The same participants wore a cooling-gel collar in the first round of tests, but not in the second. Time to exhaustion, heart rate, rectal temperature, neck skin temperature, rating of perceived exertion, and thermal sensation were measured. The researchers concluded that participants who wore the cooling-gel collars were able to exercise 13.5% longer on average before reaching their maximum level of exhaustion because the cooling collars dampened the perceived levels of thermal strain. Despite these perceptions of relief, their extended exertion did not reduce rectal temperatures or heart rates, potentially increasing the risk of heat-related illness (Tyler, 2011).
The Occupational Safety and Health Administration (OSHA), National Institute for Occupational Safety and Health (NIOSH), Center for Disease Control (CDC), other government agencies, and industry and employee groups agree that working in environments with high temperature and humidity is potentially hazardous. As a result, there have been regulations to reduce this risk. NIOSH states that management should, “Provide auxiliary body cooling vests or suits for cleaning the sniff (vent), maintenance work, or any other activity that occurs in high heat exposure areas.”
Manufacturers state that cooling vests, “maintain a comfortable temperature even in the most extreme heated environment (by) absorbing heat generated by the wearer.” In addition, manufacturers claim that cooling vests “…provide great relief for all of the symptoms of heat stress.”
Safety and health experts believe that workers will be less likely to develop heat illness if they use cooling vests while working in hot and humid conditions.
The manufacturer, RPCM, states that its cool vests will remain thermally stable at 59 °F for hours to help keep body temperature normal.
TuffRhino’s evaporative cooling vests remove body heat for 5-10 hours depending on the humidity in the atmosphere.
All MiraCool products use absorbent crystals to retain water. Using evaporative cooling methods for up to two days before re-soaking the products is recommended.
Effects on Productivity:
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).’ Cooling vests increase productivity on the worksite.
Additional Considerations:
-Engineering controls are always superior to administrative controls and personal protective equipment, where it is feasible to directly control the hazard. Engineering solutions to consider, especially for low humidity conditions, include down-blast ventilation or fans to increase evaporative cooling; evaporative cooling units for rest stations or stationary work locations, water misting or fogging for rest stations. Semi-portable or permanent air conditioning of vehicle cabs or rest locations may also be feasible, and will be more effective in high humidity conditions.
-The effectiveness of cooling clothing depends on ambient temperatures, workload and individual physiology. Therefore, engineering controls and administrative controls, such as breaks, water, and shade, should still be emphasized.
-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.
-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 more men were exposed to heat stress than women. 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. Overall, among workers in Thailand’s tropical climates, exposure to heat stress had a direct link to kidney disease (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 continue to demonstrate poor levels of hydration in the work field. 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 tested workers by administering a urine test during working hours. The results showed that greater than 70% of 710 workers indicated 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/.
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Screening Criteria for TLV for Heat Stress Exposure |
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Allocation of Work in a Cycle of Work and Recovery |
TLV (WBGT Values in Degrees Fahrenheit) |
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|
Light1 |
Moderate2 |
Heavy3 |
Very Heavy4 |
|
|
75-100% |
87.8 |
82.4 |
-- |
-- |
|
50-75% |
87.8 |
84.2 |
81.5 |
-- |
|
25-50% |
89.6 |
86.0 |
84.2 |
82.4 |
|
0-25% |
90.5 |
86.9 |
86.9 |
86.0 |
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.
-In addition, a cooling vest could be ideal for highway construction where high-visibility safety vests are required.
Contributors:
Dan Anton, PT, PhD, ATC; and Kevin Wright, SPT – Eastern Washington University
Andrew Kingston, Michael R. Cooper and Bruce Lippy – The Lippy Group
Availability
Glacier Tek
To obtain information, visit Flex Vest and Original Cool Vest
or contact 1-800-482-0533
NIOSH Workplace Solutions Sheet
The National Institute of Safety and Health (NIOSH) has published a series of “Workplace Solutions”, which are easy-to-understand recommendations from NIOSH research results. Related to this Construction Solution, please find more information on:
Preventing Heat-related Illness or Death of Outdoor Workers
Texas Cool Vest
To obtain information, visit Standard Cool Vest, High Visibility, Reflective Strips
or contact 1-713-952-1983 sales@texascoolvest.com
Arctic Heat
To obtain information, visit Cool vests, neck tie, neck wrap
or contact 1-201-632-5818 admin@arcticheatusa.com
First Line Technology
To obtain information, visit PhaseCore Cooling Vest and PhaseCore Cooling Vest video
or contact 1-703-955-7510 sales@firstlinetech.com
