SOME ASPECTS OF THE SAFETY OF AEROSOL CONTAINERS 367 (perhaps varying with the implicit hazardous properties of the fill), the suitability of a container is then simply related to the total vapour pressure ("effective working pressure" or EWP), determined at ambient and at maxi- mum temperature, of an intended formulation. Considerations such as these are being examined by the relevant B.S. committee, and already exist in the substantive or draft regulations of a number of other countries. The EWP at 50 ø is limited in Finland to 11.6, and in Germany it was 6.2, atmospheres (arm), although the latter was being reconsidered 4. In the Union of South Africa, the EWP at 55 ø for glass and plastics dispensers must not exceed 8.5 arm, or for metal dispensers, 12.2 atm. In a recent Swedish draft, three grades of dispenser are related to six groups of aerosol formula- tions and also for butane fuel containers the groups are based on EWP's at 21 ø of 3 atm, 3 to 4.2, 4.2 to 5 (if non-toxic, non-combustible), up to 6 atm for insecticides pressurized by a non-combustible compressed gas, up to 6.3 (at 21ø and 8.7 at 55 ø) for a non-toxic non-combustible concentrate pressur- ized by a compressed gas and, finally, food or soap products with a com- pressed gas with EWP's of 7 and 9 arm at 21 ø and 55 ø respectively. There is also an over-riding limit of 12 arm. In the U.S.A., a somewhat similar system of classification is employed: for EWP's measured at 21ø, no regula- tions apply below 2.7 arm, but above this value three ranges are listed: 2.7 to 3.7, 3.7 to 5 and 5 to 5.8 arm. For the two higher ranges, a particular container is specified. As will be apparent from Fig. 8, propellant 12 has a vapour pressure at 21 ø of 5-7 arm, rising to about 13.5 at 55 ø, from which it may be inferred that the extrapolated U.S. maximum EWP is higher than that allowed in the other countries mentioned. A specified proportion of dispensers (e.g. 1 in 5,000) are tested hydrauli- cally prior to filling: Sweden (minimum test 12 arm) and Finland require pressures 1« times the estimated EWP at 50 ø, and Germany a standard 9.7 arm. The Union of South Africa tests all "low pressure" containers at 9.6 arm and medium pressure (metal only) dispensers at 13.2 arm, whilst 1 per 5,000 is expected to resist 12.2 or 15.3 arm, respectively, when tested to destruction. Sweden require a similar test to destruction (for 1 in 5,000 containers) which must resist at least 18 arm. The five countries mentioned test all filled containers by immersion in a waterbath until the contents reach the temperature of 55 ø (Finland 50ø). In addition to the waterbath test at 71 ø, the CPO specification 5 requires a container to withstand 17 arm. CONCENTRATE Whilst it is possible to draw certain general conclusions as to composition from the function and details specified on the maker's label, if the potential hazards of the filled dispenser are to be assessed properly, it is imperative that the manufacturer or his agent supply, in confidence, a complete quantitative

368 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS declaration of the composition. In default of such information, a complete analysis of the concentrate is a time-consuming and expensive business which might inordinately delay a decision on a particular application. The supply of inaccurate or wilfully misleading details could result in very serious consequences if an accident subsequently occurred. Normally, such a declaration is accepted, subject to elucidation of any inherent uncertainty, but where the performance tests (see below)--which will in part be based upon this declaration--indicate any inconsistency, the containers are cooled to --30 ø , when (unless compressed gases are suspected) the dispensers may safely be cut open and the contents examined. The chilled product is fractionally distilled, and the components identified chemically, by ultra- violet and infra-red spectroscopy and by gas-chromatography. Of the four principal hazards, .flammability is considered the most serious and certain routine performance tests are invariably applied. The first test is concerned with the emitted spray, i.e. the resultant flammability of the mixture of propellant(s), solvent(s) and active ingredients this test corres- ponds roughly to the U.S. Bureau of Explosives flame projection test. A lighted taper is applied from above and from the side of the aerosol spray at distances of approximately 50, 25, 5 and 1 cm from the valve button an estimate of the flame projection is made and any tendency to strike back to the jet noted. Ethanolic concentrates typically show strong projection at 5 cm, becoming progressively diffuse and weak when tested at 25 and 50 cm. The test is repeated after shakh•g the container vigorously (for about 30 seconds) and again with the container inverted. Where a flam- mable (hydrocarbon) propellant is indicated, by declaration and/or the observed flammability of the spray of the inverted dispenser, the dispenser is discharged within a confined space (a litre beaker, over which a clock glass may be slid, is conveniently employed) and a lighted taper applied: a strong flash is observed when (say) butane is present. This small-scale qualitative test for the formation of an explosive mixture with air, although arbitrary, may be compared with the U.S. "closed drum" test. A second sequence of tests determines the combustibility of the residual components following successive evaporation of the more volatile constituents. The dispenser is discharged into an open (porcelain or silica) dish until up to 15 ml of liquid have been collected, and a lighted taper promptly applied. If the liquid fails to ignite, the test is repeated successively after «, 1« and 5 minutes (at laboratory temperature), after 5 minutes cooling following 2 minutes heating on a boiling steam bath and finally after a further 5, and then 10, minutes heating (being tested whilst still on the steam bath). This performance test on the concentrate is more searching than the U.S. (modified Tagliabue open cup) test but still makes (practical) allowance for the masking or suppression of flammability by the presence of a "quenching" component of comparable