When the heat index hits 110 degrees in a foundry or on an asphalt paving crew, evaporative cooling vests are a lifesaver. These vests are filled with super-absorbent polymer crystals. You soak the vest in water for a few minutes, the crystals swell up into a gel, and as the water slowly evaporates over the next several hours, it pulls the heat right out of your body. But there is a reason a lot of old-school guys refuse to wear them: after a week of use, they smell worse than a dead animal, and they cause terrible skin rashes.
The foul odor is not your sweat; it is a biological hazard. When a worker finishes a shift, their vest is still damp and full of warm body heat. Instead of hanging the vest up to dry completely, they usually throw it in a ball in the back of their hot truck cab or stuff it in a locker. A damp, warm polymer gel is the perfect breeding ground for mold, mildew, and anaerobic bacteria. The vest literally becomes a portable swamp. If the worker puts that bacteria-ridden vest back on the next day, the wet fabric grinds the microbes directly into their open pores, causing severe contact dermatitis or staph infections.
You must maintain an evaporative vest with the same hygiene standards as a scuba suit or a football pad. At the end of every single shift, the vest must be zipped up, hung on a hanger, and allowed to dry completely in a well-ventilated area out of direct sunlight. It cannot be folded or crumpled while drying, as this traps the moisture in the folds and guarantees mold growth.
Furthermore, the polymer crystals inside the vest have microscopic pores that get clogged with body oils, sunscreen, and dirt. When the pores clog, the crystals stop absorbing water, and the vest stops cooling. Once a week, you must hand-wash the vest in a bucket of warm water with a tiny amount of mild, antimicrobial soap. Do not machine wash it, as the agitator will shred the internal pockets and leak the toxic gel everywhere. After washing, rinse it thoroughly until the water runs completely clear. If you ever notice black spots forming inside the fabric that won't wash out, the mold has infected the gel, and the vest must be thrown away. A cooling vest is only as good as its hygiene; a stinky vest isn't just gross, it is a health hazard.
