When you buy a nylon or polyester safety harness, it is incredibly strong. The webbing can withstand thousands of pounds of force. But while this synthetic webbing is tough against physical tearing, it has a fatal, invisible enemy: ultraviolet radiation. The same UV rays that give you a sunburn are silently destroying the polymer chains inside your fall protection gear, and you probably won't be able to see it until the harness tears apart like wet paper.
The most common, deadly mistake workers make is storing their fall protection inside the cab of their work truck, hanging on the rear window or draped over the passenger seat. A truck cab in the summer acts like a greenhouse. The UV rays pour through the glass, baking the harness day after day, week after week. While some modern windshields block UVB rays, most side and rear windows allow UVA rays to pass through freely. UVA radiation penetrates deep into the synthetic fibers, causing a chemical process called photodegradation. The UV rays break the molecular bonds of the polymer chains, making the fibers brittle and weak.
A UV-damaged harness looks almost identical to a safe harness. The color might be slightly faded, but workers rarely notice fading on dirty gear. The critical test is tactile. When you run your bare hands down the webbing of a healthy harness, the material feels smooth, dense, and slightly slippery. If the webbing has been UV damaged, it will feel slightly fuzzy, chalky, or stiff. The surface of the fibers has started to fray and powder.
To test for this, take the webbing and try to flex it sharply. Healthy webbing will bend smoothly and spring back into shape. UV-damaged webbing will resist bending, and if you look closely at the crease you just made, you will see tiny white fibers popping out where the brittle, damaged fibers have snapped under the tension.
Harnesses must be stored in a dark, dry, well-ventilated room or in a dedicated gear bag when not in use. If a harness is used outdoors on a daily basis-like on a high-rise steel project-the safety manager must implement an accelerated inspection cycle, checking the webbing for stiffness and fuzziness every single week. A harness that has been baked in a truck window for a summer is a loaded weapon; it will hold a worker's weight while they walk around, but the moment they fall and the dynamic shock load hits the webbing, the UV-brittled fibers will snap instantly.
