The National Fire Protection Association (NFPA) Chapter 80 requires all internal chutes to have discharge doors that are held open with fusible links. The links must melt when the ambient temperature reaches 165 degrees. This action closes the door to stop fire from traveling up the chute and into the building. These discharge doors are available for square or round chutes in the standard sizes of 18” to 36”. The 2 types are rolling-incline (Type A) or square accordion style and are made to fit any manufacturer’s chute.
 
Discharge doors are not designed to be used to shut off the chute.