30 CFR § 57.22204 Main fan operation and inspection (I-A, II-A, III, and V-A mines).
Main fans shall be--
(a) Provided with a pressure-recording system; and (b) Inspected daily while operating if persons are underground.
Certification of inspections shall be made by signature and date.
Certifications and pressure recordings shall be retained for at least one
year and made available to an authorized representative of the
[52 FR, 24941, July 1, 1987, as amended at 52 FR 41397, Oct. 27, 1987; 60 FR 33719, June 29, 1995]