(a) All main fans shall be installed on the surface, in fire-resistant surroundings, and equipped with fire-resistant air ducts. Auxiliary fans installed underground shall be on positive intake air, in fire-resistant surroundings and in such location as to prevent recirculating the ventilating current.

(b) Approved facilities shall be provided at main fans at a point or points under observation while men are in the mine, which shall give warning of an interruption to a fan. Where such facilities are not provided an attendant shall be constantly kept on duty while men are in the mine.

(c) A daily inspection shall be made of all main fans and machinery connected therewith by a competent person and a record kept of the same in a book prescribed for that purpose.