PK Shutters offer a range of fire doors with fire ratings from 30 to 240 minutes. Fire resistance tests are undertaken by Warrington Fire research in accordance with clause 8 of BS 476: Part 22: 1987. PK Shutters fire doors are custom manufactured to greater tolerances than normal doors. Safety features may include the door closing automatically if a fire alarm has been triggered. With audio and visual sounders to alert the public that it has been activated. A fuseable link is also offered for manual roller shutter doors; this will melt and allow a door to close in the event of a fire, as it will not be connected to a fire alarm.