Anyone who runs a chainsaw in forestry, landscaping, or utility line clearance knows the importance of chainsaw safety chaps. These garments are a marvel of engineering. They are not made of impenetrable armor; instead, they are stuffed with dozens of layers of long, loose Kevlar and ballistic nylon fibers (commonly known by the brand name Avertic). When a spinning chainsaw chain strikes the chap, it instantly rips through the outer shell and pulls the loose fibers out, clogging and stalling the saw's drive sprocket in a fraction of a second, stopping the blade before it reaches your flesh.
But the Kevlar fibers that save your life are highly susceptible to a silent, invisible killer: common laundry chemicals. Specifically, chlorine bleach and highly alkaline detergents.
Kevlar is an aramid fiber. Its incredible tensile strength comes from the rigid, rod-like molecular chains inside the fiber. When you wash Kevlar chaps in bleach or harsh alkaline soap, the chemicals aggressively attack the polymer chains, literally severing the molecular bonds. The damage is completely invisible. The fabric looks exactly the same; it still feels thick and heavy. But the tensile strength of the fibers has been reduced by up to 50%. If a saw hits those chemically degraded chaps, instead of pulling out in long, strong ropes that jam the sprocket, the Kevlar will simply disintegrate into weak, powdery dust. The saw will cut right through the chaps and into your leg as if you were wearing a pair of thin cotton jeans.
Chainsaw chaps must be washed in cold water using only a mild, pH-neutral soap, with absolutely zero bleach. They must be air-dried; the high heat of a commercial dryer can also melt the internal fibers. Furthermore, you must inspect the internal pads. If the outer shell gets a small tear from a branch and you throw the chaps in the back of a dirty truck, dirt and sawdust will pack inside the pads. When the fibers are tightly packed with dirt, they can no longer pull out to clog the saw. Always store chaps hanging flat, and if the internal pads have shifted from a fall or improper storage, gently massage them back into place over the front of your thighs. Never sew through the protective pads to patch a shell; a sewing needle creates a perforated line that gives the saw a perfect path to cut through.
