Section 70-502 - Main fans installed on surface; auxiliary fans underground to be fire resistant(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.1965, Nov. 10, P.L. 721, No. 346, art. V, § 502.