(h) The use of mercury seals is prohibited.
Mercury has been found unreliable as a seal in acetylene apparatus.(i) Combustible oils must not be used in connexion with the apparatus.
(j) The construction must be such that liquid seals shall not become thickened by the deposit of lime or other foreign matter.
(k) The apparatus must be constructed so that accidental siphoning of water will be impossible.
(l) Flexible tubing, swing joints, unions, springs, mechanical check-valves, chains, pulleys, stuffing-boxes and lead or fusible piping must not be used on acetylene apparatus except where failure of such parts will not vitally affect the working or safety of the machine.
Floats must not be used excepting in cases where failure will result only in rendering the machine inoperative.
(m) Every machine must be plainly marked with the maximum number of lights it is designed to supply, the amount of carbide necessary for a single charge, the manufacturer's name and the name of the machine.
16. GENERATING CHAMBERS.--(a) Must be constructed of galvanised iron or steel not less than No. 24 U.S. Standard gauge in thickness for capacities up to and including 20 gallons, not less than No. 22 U.S. Standard gauge for capacities between 20 and 75 gallons, and not less than No. 20 U.S. Standard gauge for capacities in excess of 75 gallons.
(b) Must each be connected with the gasholder in such a manner that they will, at all times, give open connexion either to the gasholder or to the blow-off pipe to the outer air.
This prevents dangerous pressure within or the escape of gas from the generating chamber.