A relevant first-aider who has a current certificate in the use of nitrous oxide (S4) granted by a registered training organisation may –

(a) possess nitrous oxide (S4); and

(b) administer it, or supply it for self-administration, to a person, on the oral instruction of a medical practitioner; and

(c) administer it, or supply it for self-administration, to a person, on the written instruction, other than on a standing order, of a medical practitioner; and

(d) in an emergency, administer it, or supply it for self-administration, to a person, without instruction from a medical practitioner.