Explosive Atmospheres - Part 2: Equipment Protection by Pressurized Enclosure "p"
UL 60079-2
1 Scope

This part of IEC 60079 standard contains the specific requirements for the construction and testing of electrical apparatus with pressurized enclosures, of type of protection "p", intended for use in explosive gas atmospheres hazardous (classified) locations defined as Class I, Zone 1 or Zone 2 by the National Electrical Code (NEC®), ANSI/NFPA 70. It specifies requirements for pressurized enclosures containing a limited release of a flammable substance.

This standard supplements and modifies the general requirements of IEC ANSI/ISA-60079-0.Where a requirement of this standard conflicts with a requirement of IEC ANSI/ISA-60079-0, therequirements of this standard takes precedence.

This standard does not contain the requirements for:

• pressurized enclosures where the containment system may release
  a) air with an oxygen content greater than normal, or
  b) oxygen in combination with inert gas in a proportion greater than 21 %;
• pressurized rooms or analyser houses; see IEC 60079-13 and IEC 60079-16.

NOTE 1 Due to the safety factors incorporated in the type of protection, the uncertainty of measurement inherent in good quality, regularly calibrated measurement equipment is considered to have no significant detrimental effect and need not be taken into account when making the measurements necessary to verify compliance of the equipment with the requirements of this standard.

NOTE 2 When the user acts in the role of the manufacturer, it is typically the user's responsibility to ensure that allrelevant parts of this standard are applied to the manufacturing and testing of the equipment.

NOTE 3 Types of protection "px" and "py" provide Equipment Protection Levels (EPL) Mb or Gb. Type of protection "pz" provides Equipment Protection Level (EPL) Gc. For further information, see Annex H.