The operation of the chamber
10. The occupier of a slaughterhouse at which a chamber is used and any person engaged in the killing of birds by exposure to the gas mixture shall ensure that—
(a)any bird which arrives at the installation in a transport crate and which is removed from the crate before it enters the chamber is handled with care and in such a way that the bird is not caused avoidable pain or suffering;
(b)no bird enters the chamber if, as appropriate—
(i)the displayed concentration of oxygen is above 2% by volume, except that the concentration of oxygen may occasionally rise to a concentration of not more than 5% by volume for not more than 30 seconds; or
(ii)the displayed concentration of carbon dioxide is below 25% by volume or above 30% by volume;
(c)no bird is passed through or allowed to remain in the chamber at any time when the visible and audible warning signals provided for in paragraph 8(c)(iii) above have been activated or when there is any defect in the operation of the chamber; and
(d)no bird is shackled before it is dead.