NFPA 1951 Performance Requirements
This standard was initially formed for USAR (Urban Search & Rescue) gear, and was based on the 1993 U.S. Fire Administration Study “Protective Clothing and Equipment Needs of Emergency Responders for Urban Search and Rescue Missions” published by FEMA.
In the 2nd Edition, this standard was renamed and broken down in to 3 different types of "Technical Rescue" gear. The 1st level being a "utility ensemble" that's incredibly breathable as to avoid heat stress and exhaustion, yet still provides an outer layer of protection and flame resistance. The 2nd level is a "rescue and recovery ensemble", providing the same protection as the first but including a blood-borne-pathogen barrier. Fire-Dex manufactures gear certified to the 1st and 2nd level. The third level in the standard is a CBRN ensemble.