So I have never looked into fire resistant thread. But traditionally you wear the strap underneath your bunker gear. This protects its from direct heat and water plus other harms. Also helps keep carcinogens off leather also. My strap has been through probably 10 to 12 fires and never had a problem. Our radios hold up well. I think they are rated for 500 to 600 degrees and the collar mics are usually first to fail. I have personally never had this happen.