UL 10B vs UL 10C: Why Positive Pressure Compliance Matters
Global architectural specifications increasingly require compliance with UL 10C (Positive Pressure Fire Tests of Door Assemblies) rather than legacy UL 10B (Neutral Pressure) standards. Under UL 10C testing, the neutral pressure plane is established at 40 inches above the sill, creating positive pressure in the upper portion of the furnace chamber. This forces hot gases and flames toward perimeter joints, testing the actual sealing performance of intumescent gaskets and frame designs. At Guangdong Derki Doors & Windows Technology Co., Ltd., our UL Fire Rated Door systems integrate expanding intumescent seals that form a rigid, non-combustible barrier up to 180 minutes under positive thermal stress.







