Except for small quantities, calcium carbide cannot be stored without a licence being first obtained. This means that an acetylene generating apparatus, when fixed for use, necessitates a licence being obtained, as the apparatus is useless without a store of carbide; and the quantity of this latter material which may be stored without a licence (namely, 5 lbs. in five 1 lb. tins withoutanyconditions, or281bs. under special conditions) is too little for even a small residence plant. This being realised, it is a good plan to apply for the licence before the apparatus is erected, as the granting of a licence necessitates the attendance of the surveyor to the local authorities, and he will at once say if the location of the proposed store is to his approval. The importance of this arrangement is that the work cannot be condemned afterwards, and as the carbide store and the generator house are one and the same building (in all except very large undertakings) the whole obtain official sanction and approval at once. In building the generator house, space should be allowed for a sufficient store of carbide to prevent the possibility of running short. It should be arranged that one drum (1 cwt.) should always be in store untouched by the normal demand. The charge for the licence, payable yearly, is 5s. or any less sum. Occasionally 2s. 6d. only is charged. This includes the surveyor's visit.

1 Notwithstanding the high degree of purity of the ingredients now used in the manufacture of carbide, purification of the resulting gas is necessary.

The carbide store (and generator house) is not allowed to be in or under any dwelling-house or similar building. It lies within the surveyor's power to allow the store to be a lean-to against a house, but it is seldom permitted. It must not be near any forge or fire or source of danger of this kind. It must be built wholly of incombustible material. (Surveyors exercise judgment in this, and commonly allow a wooden house, with brickwork foundation). It must be provided with "adequate means of ventilation." No inflammable materials may be kept in this store. The store must be kept locked at all times when not being actually used.

Remembering the carelessness of outdoor servants, farm hands, and others who usually attend to the generator, it is wise to adopt every possible precaution against explosion. A bold notice should be painted on the door to warn everyone that naked lights must on no account be taken into or near the store; nor may smoking be allowed there, as acetylene can be ignited by glowing tobacco - pipe, cigar, or cigarette.