This standard specifies the construction and testing of intrinsically safe apparatus intended for use in an explosive atmosphere and for associated apparatus, which is intended for connection to intrinsically safe circuits which enter such atmospheres. This type of protection is applicable to electrical equipment in which the electrical circuits themselves are incapable of causing an explosion in the surrounding explosive atmospheres. This standard is also applicable to electrical equipment or parts of electrical equipment located outside the explosive atmosphere or protected by another Type of Protection listed in ANSI/ISA- 60079-0 where the intrinsic safety of the electrical circuits in the explosive atmosphere may depend upon the design and construction of such electrical equipment or parts of such electrical equipment. The electrical circuits exposed to the explosive atmosphere are evaluated for use in such an atmosphere by applying this standard. The requirements for intrinsically safe systems are provided in ISA-60079-25 IEC 60079-25. This standard supplements and modifies the general requirements of ANSI/ISA-60079-0 IEC 60079-0, except as indicated in Table 1. Where a requirement of this standard conflicts with a requirement of ANSI/ISA-60079-0 IEC 60079-0, the requirements of this standard shall take precedence. If requirements in this standard are applicable to both intrinsically safe apparatus and associated apparatus the term "apparatus" is used throughout the standard. This standard is for electrical equipment only; therefore the term "equipment" used in the standard always means "electrical equipment". If associated apparatus is placed in the explosive atmosphere, it shall be protected by an appropriate Type of Protection listed in ANSI/ISA-60079-0 IEC 60079-0, and then the requirements of that method of protection together with the relevant parts of ANSI/ISA-60079-0 IEC 60079-0, also apply to the associated apparatus.