While EPDM (ethylene propylene diene monomer) is generally safer than some other rubbers, its safety depends entirely on the cure system and additives . NSF 383 tests the final compounded product , not just the base polymer.

Elias checked the satellite logs. There were no planes, no weather balloons, and no known orbital debris in that sector. Yet, according to his sensors, something the size of a city was hovering three hundred miles up, perfectly stationary, vibrating at a frequency that shouldn't exist. Then, the clicking stopped.