There shall be no openings into any still; except those in connection with the charging and discharging pipes, pipes for the conveyance of various fluids from one part of the still to another condensors, mandoors and air cocks or valves upon the breast or head. The external orifice of an air valve must be so constructed and covered by a perforated metal plate, as to make it impracticable by means of it either to introduce wash or to abstract spirit or to convey away, spirit vapour for condensation elsewhere.
