This standard contains the specific requirements for pressurized enclosures, type of protection "p", intended for use in hazardous (classified) locations defined as Class I, Zone 1 or Zone 2 by the National Electrical Code (NEC^®), ANSI/NFPA 70.

The requirements contained in this standard are supplementary to those in ANSI/ISA- 12.00.01 (IEC 60079-0 Mod).

This standard specifies requirements for pressurized enclosures containing a limited release of a flammable substance.

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%.

This standard does not contain requirements for pressurized rooms or analyser houses.

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 apparatus with the requirements of this standard.

When the user acts in the role of the manufacturer, it is the user's responsibility to ensure that all relevant parts of this standard are applied to the manufacturing and testing of the apparatus.