(2)Notwithstanding anything contained in this rule, use of soldering apparatus or other means involving flame, fire or heat or use of industrial type apparatus in a zone "1" area shall be permitted for the purposes of effecting repairs and testing and alterations, provided that the area in which such apparatus or wiring has been installed, has first been made safe and certified by a competent person after testing with an approved gas-testing apparatus to be safe and free from inflammable vapours, gases or liquids and is maintained in such conditions, so long as the work is in progress.
