CO HSE
Approval by HSE
Every landlord shall ensure that any work in relation to a relevant gas fitting or any check of a gas appliance or flue is carried out by, or by an employee of, a member of a class of persons approved for the time being by the Health and Safety Executive.
CO HSE
https://plumobsidian.github.io/p/3391ebedda4342d39546607b2dbaca32/