Welding and cutting and other processes involving direct application of flame shall not be carried on in any garage housing more than twenty automobiles on any floor unless the garage is equipped with an approved automatic sprinkler system or such processes are carried on in a room enclosed by walls and ceiling of construction having a fire-resistance rating of not less than one hour with openings therein protected by approved fire doors or fire windows, and with no opening from such room to any upper story. No repairs of any kind shall be made in any garage the floor of which is more than two feet below the drive-in entrance level.