(1) The blow valve of a digester must be arranged so as to be operated from another room, remote from safety valves.

(2) Heavy duty pipe, valves, and fittings must be used between the digester and blow pit, blowtanks and dumptanks. These valves, fittings, and pipes must be inspected at least semiannually to determine the degree of deterioration and should be replaced when necessary.

(3) Digester blow valves or controls must be pinned or locked in closed position throughout the entire cooking period.

(4) Test holes in blow lines of piping systems must not be covered with insulation or other materials.