16. Mercury pressure gauges are prohibited. Liquid gauges, if used must be double the length normally needed, and with a cock which in automatic apparatus must be kept shut while it is in action. 17. Proper steps must always be taken to prevent the apparatus freezing. In the absence of other precautions water-seals and pressure-gauges must be filled with liquid having a sufficiently low freezing-point and without action on acetylene or the containing vessel. 18. Signal devices to show the position of the gasholder bell must not be capable of producing sparks inside the apparatus house. 19. Leaks must not be sought for with an open flame and repairs requiring the use of a blow-pipe, &c., must only be carried out after the apparatus has been taken to pieces or freed from gas by flooding. 20. Apparatus must only be attended to by trustworthy and responsible adults. 21. Portable apparatus holding not more than 1 kilo. of carbide and of not more than 50 litres per hour productive capacity, and apparatus fixed and used out of doors are exempt from the foregoing regulations except Nos. 11 and 12, and the first part of 13. In regard to (_b_), plant houses, it is enacted that: 1. Rooms containing acetylene apparatus must be of ample size, used for no other purpose, have water-tight floors, be warmed without fireplaces or chimneys, be lighted from outside through an air-tight window by an independent artificial light, have doors opening outwards, efficient ventilation and a store of sand or like material for fire extinction. Strangers must be warned away. 2. Apparatus of not more than 300 litres per hour productive capacity may be erected in basements or annexes of dwelling houses, but if of over 50 litres per hour capacity must not be placed under rooms regularly frequented. Rooms regularly frequented and those under the same must not be used. 3. Apparatus of more than 300 litres per hour productive capacity must be erected in an independent building at least 15 feet distant from other property, which building, unless it is at least 30 feet distant, must be of fire-proof material externally. 4. Gasholders exceeding 280 cubic foot in capacity must be in a detached room or in the open and inaccessible to strangers, and at least 30 feet from other property and with lightning conductors. 5. In case of fire the main cock must not be shut until it is ascertained that no one remains in the room served with the gas. 6. All acetylene installations must be known to the local fire brigade. In regard to (_c_), pipes, it is enacted that: 1. Mains for acetylene must be separated from the generating apparatus by a cock, and under a five-minute test for pressure must not show a fall of over eight-tenths inch when the pressure is 13.8 inches, or three times the working pressure, whichever is greater.