UL 723 (ASTM E84) and ULC S102.2 are two different test methods for measuring the surface burning characteristics of building materials. While both methods use the same Steiner Tunnel apparatus, they have different sample mounting procedures which can result in different flame spread and smoke developed index values. ULC S102.2 is designed to test materials mounted in both ceiling and floor positions, whereas UL 723 only tests in the ceiling position. U.S. building codes require materials used in air-handling spaces to have a flame spread index of 25 or less and a smoke developed index of 50 or less when tested by UL 723. The document cautions that assuming compliance based on ULC S102.2