3. All water-seals must be carefully kept full.
4. When any part of an acetylene apparatus or a gas-meter freezes, notwithstanding the precautions specified in II., 7, it must be thawed only by pouring hot water into or over it; flames, burning fuel, or red- hot iron bars must not be used.
5. Alterations to any part of an apparatus which involve the operations of soldering or riveting, &c., i.e., in which a fire must be used, or a spark may be produced by the impact of hammer on metal, must only be carried out by daylight in the open air after the apparatus has been taken to pieces. First of all the plant must be freed from gas. This is to be done by filling every part with water till the liquid overflows, leaving the water in it for at least five minutes before emptying it again.
6. The apparatus house must not be used for any other operation, nor employed for the storage of combustible articles. It must be efficiently ventilated, and always kept closed. A notice must be put upon the door that unauthorised persons are not permitted to enter.
7. It in forbidden to enter the house with a burning lantern or lamp, to strike matches, or to smoke therein.
8. A search for leaks in the pipes must not be made with the aid of a light.
9. Alterations to the service must not be made while the pipes are under pressure, but only after the main cock has been shut.
10. If portable apparatus, such as described in I., 12, are connected to the burners with rubber tube, the tube must be fortified with an internal or external spiral of wire. The tube must be fastened at both ends to the cocks with thread, copper wire, or with ring clamps.
11. The preparation, storage, and use of compressed or liquefied acetylene is forbidden. By compressed acetylene, however, is only to be understood gas compressed to a pressure exceeding one effective atmosphere. Acetylene compressed into porous matter, with or without acetone, is excepted from this prohibition.
12. In the case of plants serving 50 lights or less, not more than 100 kilos. of carbide in closed vessels may be kept in the apparatus house besides the drum actually in use.