1DV DR Modification of Clause 1 to replace with the following: This standard contains the specific requirements for the construction and testing of electrical equipment with pressurized enclosures@ of type of protection ??p??@ intended for use in explosive gas atmospheres or explosive dust atmospheres. It also includes the requirements for pressurized enclosures containing a limited release of a flammable substance. This standard supplements and modifies the general requirements ofUL 60079-0. Where a requirement of this standard conflicts with a requirement ofUL 60079-0@ the requirements of this standard take precedence. This standard does not include 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 where the oxygen is in a proportion greater than 21 %. ? pressurized rooms or analyser houses; see IEC 60079-13; ? pressurized enclosures used where ??explosives?? or pyrotechnics are present; ? pressurized enclosures used where hybrid mixtures of gas/vapour and combustible dust are present; ? pressurized enclosures used where pyrophoric substances such as explosives or propellants containing their own oxidizers are present ? pressurized enclosures with an internal source of release of combustible dust. NOTE When the user acts in the role of the manufacturer@ it is typically the user??s responsibility to ensure that all relevant parts of this standard are applied to the manufacturing and testing of the equipment. Where references are made to other IEC 60079 standards@ the reference requirements found in these standards apply as modified by any applicable U.S. National Differences.