UL 60079-13-2020 pdf download – Explosive Atmospheres – Part 13: Equipment Protection by Pressurized Room “p” and Artificially Ventilated Room “v”.
4.2 Type and level of protection 4.2.1 Pressurization “p” Rooms with pressurization “p” and located in a hazardous area shall be one of the following: a) Level of protection “pb” (EPL Gb or Db). The pressurized room maintains an internal overpressure reducing the risk of ingress of an explosive atmosphere and is suitable for use in an area requiring EPL Gb or Db, permitting unprotected equipment to be installed within the pressurized room except for pressurization safety devices (see 6.3.1). b) Level of protection “pc” (EPL Gc or Dc). The pressurized room maintains an internal overpressure reducing the risk of the ingress of an explosive atmosphere and is suitable for use in an area requiring EPL Gc or Dc, permitting unprotected equipment to be installed within the pressurized room except for pressurization safety devices (see 6.3.1). 4.2.2 Artificial ventilation “v” The artificial ventilated room maintains artificial ventilation to dilute a release of flammable substance to reduce a hazardous area inside such that the required EPL is reduced from either Gb or Gc to non- hazardous or from Gb to Gc. Rooms with artificial ventilation “v” and located in a hazardous area shall be: • level of protection “vc” (EPL Gc). The ventilated room maintains artificial ventilation to dilute a release of flammable substance to reduce a hazardous area such that unprotected equipment can be installed within the artificially ventilated room, and is suitable for use in an area requiring EPL Gc. NOTE This permits equipment with a lower EPL to be installed within the artificially ventilated room except for ventilation safety devices (see 7.3.1). Rooms may be protected by either general or local artificial ventilation. General artificial ventilation applies to an entire room or significant portion of a room and local artificial ventilation applies to restricted regions, for example an extraction hood.