UL 109

Tube Fittings for Flammable and Combustible Fluids, Refrigeration Service, and Marine Use
standard by Underwriters Laboratories, 06/19/1997

UL 60079-29-4

Explosive Atmospheres – Part 29-4: Gas Detectors – Performance Requirements of Open Path Detectors for Flammable Gases
standard by Underwriters Laboratories, 08/24/2018