Section 57.22207 - Booster fans (I-A, II-A, III, and V-A mines)(a) Booster fans shall be approved by MSHA under the applicable requirements of 30 CFR part 18, and be- (1) Provided with an automatic signal device located so that it can be seen or heard by a person designated by the mine operator to give an alarm when the fan stops or when methane reaches the following levels:(i) 1.0 percent at the fan in Subcategory I-A, Category III, and Subcategory V-A mines; and(ii) 0.5 percent at the fan in Subcategory II-A mines.(2) Equipped with a device that automatically deenergizes power in affected workings should the fan stop; and(3) Equipped with starting and stopping controls located at the fan and at another accessible remote location.(b) Booster fan installations, except for booster fans installed in ducts, shall be- (1) Provided with doors which open automatically when all fans in the installation stop; and(2) Provided with an air lock when passage through the fan bulkhead is necessary.