SOME ASPECTS OF THE SAFETY OF AEROSOL CONTAINERS 379 Falve heads. All tinplate and aluminium containers, even the slim 1 oz size, that have been examined, incorporate a standard valve insert housed in a cup of 25 mm diameter. The plastics-covered glass dispensers normally have a specially designed valve head. For space sprays and most surface sprays, the typical 0 and 11 mm cylindrical polyethylene actuator buttons, with 0.5 mm orifices, are generally fitted occasionally a spatulate button occurs. Paint and other sprays of similar particle size (not "aerosols" in the strict definition) are dispensed through a coarser valve, with a breakup device in the button a wide angle orifice may be fitted or sometimes a special "Howitzer" style button. Containers for foam forming preparations, such as shaving creams, a•e fitted with so-called "cream spouts" with an external orifice of about 8 mm. An alternative actuator operates the valve by a disc-lever through which the foam passes to the "cream spout". The valve head is inserted in a standard 25 mm stamped tinplate cup, fitted with a rubber grommet and crimped to the domed end of the case the crimped shoulder has an outside diameter of about 32 mm. Where a con- tainer has leaked during heat storage, on only one occasion has it been evident that the grommet had been displaced. Aluminium cups would be considered desirable for insertion in aluminium cases, to avoid electrolytic corrosion, but none has been observed. Inspection suggests that frequently the height of the top of a standard 11 mm actuator button above the domed shoulder is greater (about 23-24 mm) for 12 oz dispensers than (10-20 mm) for the 6 oz variety. Since a maker may often use the same caps for both sizes, it follows that the internal clearance above the button will be significantly less for the larger container, and may lead to the anomalous conclusion that a given cap is not satisfactory for all sizes of an apparently similar!y con '• structed dispenser. The same anomaly arises with some paint dispensers, where the valve cup may have a taller boss. Another cause of failure adequately to resist an applied load, the splaying of the fluted walls of a polyethylene cap, is usually found with slim containers (e.g. the 35 mm diameter, 1 oz dispensers), or where the domed shoulder of the case slopes steeply away from the cup rim in such an event, a sturdy tinplate cap is the better fitting. Reference has already been made to a conical cap which splays more readily on the shoulders of the slender (up to 8 oz) dispensers. TRANSPORT RESTRICTIONS Applications for carriage by sea are scrutinized in the manner outlined in the preceding sections in order to assess the hazards that might be offered "to ship or crew" by the container and its contents. If for any reason the proposed packing is considered to furnish inadequate protection, modifica- tions are suggested. Where possible, an application is related to a product of similar type for which the Minister of Transport's Standing Advisory

380 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Committee has already approved a packing and/or one which has an estab- lished safety record. Existing precedents are observed in stowage restric- tions which are based on experience of application of the Safety Rules. Labelling and Declaration are the least clearly defined aspects. Advice on questions of stowage and packing may be sought through the Ministry of Transport from their Marine Surveyors and, in the ultimate, any substantive doubt as to whether an existing provision can safely be relaxed is referred to the Standing Advisory Committee. Occasionally, a product can be recommended as offering no significant hazard to ship or crew and may then be declared as "non-hazardous" (as, for example, an aqueous non-flammable emulsion pressurized by only 6% of propellant 12 or by an inert compressed gas). More often, such a packing can be recommended that enables a product to be described as "non- hazardous when packed as proposed", although it may be necessary to add certain provisions as to stowage. If the composition of the product is not sufficiently hazardous to warrant specific declaration under an appropriate entry in the "Blue Book "•, (e.g. large quantities of Toxic--Section 4, or Flammable--Section 5, substances when the dispensers would have to be packed, stowed and labelled accordingly), the product might nevertheless be classified under Section 10 ("Other Dangerous Goods") of the "Blue Book", labelled as "Low Pressure Aerosol Dispensers" and stowed as specific- ally recommended. Recommendations for packaging, stowage and labelling are conveniently summarized according to the hazard concerned. Unless the composition is regarded as completely non-hazardous a general restriction is suggested concerning stowage in the vicinity of strong acids (for tinplate containers), and also of strong alkalies ({or aluminium containers). Plastics-covered glass dispensers are usually packed in outer wooden cases and, of course, recommended to be stowed away from external sources of heat. Where one or more containers show significant evidence of leakage or visible distortion following 18 hours' storage at 55 ø , further samples, from different batches if possible, are sought and tested. Containers that burst open at the seam or persistently leak are not normally considered suitable for carriage through tropical conditions. If conveyance in temperate latitudes only (as defined above) is then sought, fresh samples are tested at 45 ø . Dispensers that have failed on heat storage may still be carried subject to consideration of the contents. If chlorofluoroa!kane propellants consti- tute the principal hazard (cf. the comments on asphyxia and lethal con- centrations in the section on propellants), storage "on deck only" in wooden outers, has been suggested. Where potentially more dangerous components are present, the risk to ship or crew associated even with "on deck" stowage must be evaluated.