Ohmweve resistors are woven from a high temperature yarn made of fiberglass, Kevlar and Kynol. The first time the resistors are used, the Kevlar and Kynol will burn off leaving the glass fiber. After burn-off, the resistors will be smoke free and retain their original strength. Note: smoke from ANY source can be unhealthy and we suggest performing burn-off in a well ventilated area with fans or ducts to guide the smoke away from personnel.