The operation of the chamber
6. The occupier of a slaughterhouse at which a chamber is used and any person engaged in the killing of pigs by exposure to carbon dioxide shall ensure that—
(a)no pig enters the chamber if the displayed concentration by volume of carbon dioxide in the gas mixture falls below 70%; and
(b)no pig is passed through or allowed to remain in the chamber at any time when the visible and audible warning signals provided for in paragraph 4(e)(iii) have been activated or when there is any defect in the operation of the chamber.