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The Essence of Cold Weather Protection
As the seasons change, we are used to adjusting our everyday wardrobes to combat dwindling temperatures. For workers such as those in the oil and gas and utility industries, who may face long periods of exposure to the outdoors, transitioning work wear for the changing seasons is just as important.
Long hours outdoors leaves workers susceptible to cold stress and related illnesses. Similar to heat stress, cold stress occurs when someone begins to lose the ability to regulate his or her body temperature during prolonged exposure to extreme temperatures, in this case to the cold. This can lead to a decrease in productivity and performance. As core body temperature drops, various stages of hypothermia occur, which can cause workers to lose coordination and experience a decrease in breathing and heart rate. How the cold affects a worker can depend on many factors, including medications, pre-existing conditions, and body composition. (Princeton University, 2018)
For workers who face arc flash or flash fire hazards, combating the cold may not be as simple as throwing a favorite jacket over their FR gear, but dressing for cold doesn't have to be complicated. First, remember it's important to follow the safety protocols outlined by employers. Any outer layer added over FR uniforms also needs to be FR and compliant to the standards appropriate for protection against potential hazards. Just as with any other hazard, education is a key step in mitigating cold stress.
As soon as core temperature begins to drop, mild hypothermia occurs and brings common symptoms such as shivering, lack of coordination, stumbling, fumbling, and slurred speech. When you're in a cold environment, most of your body’s energy is used to keep your internal temperature warm. (Princeton University, 2018) When you’re busy trying to keep warm, it can be very difficult to focus on getting the job done. Preparing workers for their environmental conditions not only works to help keep them safe, but also it helps maintain productivity levels. Acclimating workers to cold exposure, hydration, scheduling frequent breaks, and equipment such as heaters are all part of the prevention process. (Dorsey, 2018)
According to OSHA, "[d]ressing properly is extremely important to preventing cold stress." The agency's Cold Stress Guide provides information for employers to prepare their team for coming months. Some of OSHA's recommendations for dressing for the cold are using light, loose layers that allow for ventilation and including a moisture-wicking layer against the skin. (OSHA, 2018) These recommendations align with end user research that has identified the top three characteristics of a comfortable garment as lightweight, breathable, and moisture wicking.
Comfort is Key
Comfort is a contributing factor to workers' willingness to wear their PPE for compliance. An ISEA/VPPPA survey of safety professionals conducted in 2016 identified these top hurdles to getting wearers to wear their PPE: lack of comfort, too hot, and poor fit. Providing garments that workers want to wear is key to gaining buy-in and cooperation with safety standards. Lightweight, breathable, and moisture wicking are characteristics commonly talked about during the warmer months in regard to staying cool and comfortable, but the same science can be applied to keeping the body warm and comfortable in the cold.
Maintaining comfort in winter is centered on keeping the body warm. Lightweight garments may seem counterintuitive for protecting against the cold, but layering up lightweight garments is one of the best ways to combat the cold and remain comfortable. The secret to layering is the air gap between layers, which provides excellent insulation. This air insulation is also what results in most layered systems arc testing much higher than the individual garment ratings added together. Layering allows wearers to adjust their level of protection as the environmental conditions change throughout the day. Another benefit of increasing warmth by adding lightweight layers is mobility. Instead of adding one heavy layer on top of regular daily wear, lightweight layers are less likely to have a negative impact on mobility and comfort than a bulky, heavy, outerwear garment. For workers doing light physical activity in extreme cold environments, a heavy outerwear piece may make more sense. Workers in moderate to substantial physical activity jobs will benefit from this light layering principle to avoid overheating.
The Importance of Moisture Wicking
Garments that contribute to overheating can actually end up making the wearer feel colder. How is this possible? Overheating due to bulky outerwear can cause excessive sweating, leaving the garments and skin feeling damp. According to OSHA, dampness can quickly accelerate heat loss, dropping skin temperature and contributing to cold stress. (OSHA 2018) For this reason, breathable, moisture-wicking clothing is recommended in cold environments. Garments that wick and breathe are less likely to contribute to overheating during physical activity, thus keeping the wearer dryer for a longer period of time.
Combining light layers is important to maintaining warmth, but what you layer together matters. Garments such as 100 percent cotton are not recommended by OSHA because they retain moisture, making them less effective at insulating and more likely to accelerate heat loss. Staying dry during colder months plays a key role in reducing the risk of cold stress and hypothermia. According to the CDC, "While hypothermia is most likely at very cold temperatures, it can occur even at cool temperatures (above 40º F) if a person becomes chilled from rain, sweat, or submersion in cold water." (CDC, 2016) A moisture-wicking base layer is great for pulling moisture away from the body, but if the next layer does not have the same performance, moisture can either get trapped in that garment or between the layers, leaving the wearer feeling damp and uncomfortable. Combining high-performance work wear for all layers allows the garments to consecutively move the moisture away from the body in order to keep wearers and their clothing dry and warm.
Moisture wicking is the process in which a fabric pulls moisture away from the skin and then pushes that moisture out to the surface of the fabric. When the layering system is made up of moisture-wicking fabrics, moisture is transferred though the layers out to the surface, where it can dry quickly. This push-pull can be achieved in two ways. One is a treatment or finishing technique that can be applied to a fabric. This performance typically lasts a certain number of launderings, and effectiveness decreases with wash and wear of the garment. The other way to achieve this push-pull process is to start at the fiber level and engineer a moisture-wicking fabric for permanent performance.
Fibers that naturally absorb water easily are called hydrophilic. Common water-loving fibers are cotton, wool, and rayon. Alternatively, there are some fibers that naturally resist or push water away. These are referred to as hydrophobic, or water-hating fibers. Modacrylic, polyester, and nylon are common hydrophobic fibers. Combining both types of fibers will result in a fabric that will absorb perspiration but then be able to release it quickly so it can evaporate. Using the right combination of hydrophilic and hydrophobic fibers can result in a fabric that dries three to four times faster than cotton. This fast dry process means that the wearer will stay dry and more comfortable. In the case of winter layering, this can mean a decreased rate of heat loss.
Layering the Right Way
Remember that compliance with the appropriate protective standard should always be included in selecting PPE, regardless of what the weather brings. Additional layers added to a typical FR uniform also need to be FR and comply with those same standards. Topping everyday FR PPE with a garment that can't stand up to your potential hazard can contribute to and exacerbate injuries in the event of an accident. After appropriate protection against regulated hazards has been confirmed, be sure to consider protection against the climate, both heat stress and cold stress.
1. Centers for Disease Control and Prevention. (2016, December). Hypothermia. Retrieved from https://www.cdc.gov/disasters/winter/staysafe/hypothermia.html
2. Centers for Disease Control and Prevention. (2016, December). Stay Healthy in Cold Weather. Retrieved from https://www.cdc.gov/disasters/winter/staysafe/index.html
3. Dorsey, A. R. (2018, February). Preventing Cold Stress While Working Outdoors. Retrieved from Laborers' Health & Safety Fund of North America: https://www.lhsfna.org/index.cfm/lifelines/february-2018/preventing-cold-stress-while-working-outdoors/
4. OSHA. (2018, September). Cold Stress Guide. Retrieved from Occupational Safety and Health Administration: https://www.osha.gov/SLTC/emergencypreparedness/guides/cold.html
5. Princeton University. (2018, October). Princeton University EHS. Retrieved from Cold Stress Facts: https://ehs.princeton.edu/workplace-construction/occupational-health/heat-cold-stress/cold-stress-facts
This article originally appeared in the December 2018 issue of Occupational Health & Safety.