Fall arrest harnesses are made of high-strength polyester or nylon webbing. In the minds of workers, this material is indestructible canvas. But the webbing is a woven structure of thousands of individual fibers, and it has a mortal enemy: grit.
A harness worn in a steel fabrication shop, a gravel pit, or a concrete plant inevitably gets dragged in the dirt, soaked in oil, and covered in concrete slurry. The problem is not the dirt on the surface; it is the dirt trapped inside the weave. The silica grit from concrete, metal shavings from grinding, and sand from the ground work their way deep into the spaces between the fibers.
When the worker climbs, adjusts their gear, or, most critically, when they fall and arrest, the webbing stretches and elongates rapidly. Under this tension, the grit acts like microscopic sandpaper. The trapped particles grind against the individual fibers, shearing them one by one. This is called internal abrasion. From the outside, the webbing looks fuzzy or faded, but structurally, the load-bearing fibers have been cut to a fraction of their original strength.
A worker falls, and the harness, loaded with mud, snaps at the stress point because the internal integrity is gone. Maintenance is critical. You must inspect the webbing by gently flexing it to separate the fibers. Look for "fuzzing" where the fibers are breaking on the surface, or hard, gritty lumps inside the weave. Never wash a harness in a washing machine-the agitation destroys the fibers. Wash it by hand with mild soap and water, scrubbing the webbing to lift out the abrasive grit. If the webbing is stiff, heavily stained, or feels like it has internal grit that won't wash out, the harness must be destroyed. A clean harness is a strong harness; a dirty harness is a broken strap waiting to drop you.
