(2)All electric apparatus installed or used in a zone "1" area shall be either-(i)a flame proof or intrinsically safe apparatus of a type or types approved in writing by the Chief Controller, or(ii)an industrial-type apparatus housed in an enclosure or a room which has been made safe by pressurising or purging with a plenum of atmosphere free from significant concentration of any inflammable gas or vapour and so arranged and inter-locked that in case of failure of the pressurising or purging agent, the electricity supply is automatically cut off or a warning is automatically given to a person in attendance who shall take suitable measures to prevent a hazard.
