Fire Rated Access Doors.

Fire-rated access doors differ in terms of fire resistance, a value derived during a fire endurance test. Fire resistance is expressed in units of time, but may also incorporate other considerations. There are two types of fire-rated access doors: insulated and non-insulated. Insulated products are used to provide access to utilities in areas, such as stairwells, where fire ratings must be considered. Typically, several inches of insulation are sandwiched between the inside and outside door panels. Non-insulated, fire-resistant access doors are also available. Like insulated models, these products may comply with standards from Underwriters Laboratories (ULC). There are two main UL approvals for access doors. They are designated as B or ULB, and C or ULC.