A method of killing flying insects which method comprises spraying into the air in which insects are flying liquid droplets of an insecticidal composition, a unipolar charge being imparted to the said liquid droplets by double layer charging and charge separation during spraying, the unipolar charge being at a level such that the said droplets have a charge to mass ratio of at least +/-1.times.10.sup.-4 C/kg. An aerosol spray device which is capable of imparting a unipolar charge by double layer charging and charge separation to liquid droplets of a composition sprayed therefrom has a spraying head in the form of an insert in an actuator, the spraying head having a bore through which liquid is expelled having an outlet, preferably with a tortuous periphery, having an L/a ratio of at least 8 (preferably at least 10) where L is the length of the periphery defining the bore outlet in mm and a is the cross-sectional area of the bore outlet in mm.sup.2 and the apparatus being constructed such that the droplets are expelled from the spraying head at a flow ratio of at least 0.4 (preferably at least 0.5) grams per second and have a charge to mass ratio of at least +/-1.times.10.sup.-4 C/kg.

A spraying device for dispensing electrostatic liquid droplets includes a container holding a liquid at one end, and having a nozzle assembly with an aperture at another end. The nozzle assembly includes a longitudinal hollow tube terminating in a metallic structure. The metallic structure includes a metallic base plate having at least one aperture formed therein for fluid communication with the hollow tube. The longitudinal hollow tube includes an end inserted in the liquid. A charge accumulator disposed in the liquid accumulates electrostatic charges. A wire conductor between the base plate and the charge accumulator transfers the electrostatic charges from the liquid to the nozzle assembly.

A method of reducing the droplet sizes of a composition sprayed from an aerosol spray device comprising a compressed gas propellant, which method comprises imparting a unipolar charge to the liquid droplets by double layer charging during the spraying of the liquid droplets from the aerosol spray device, the unipolar charge being at a level such that the said droplets have a charge to mass ratio of at least +/-1.times.10.sup.-4 C/kg.

A personal product comprising a liquid cosmetic composition and a hand-held electrostatic spraying device suitable for applying the composition to the human body, said hand-held electrostatic spraying device comprising a slit nozzle having a maximum width of from 0.05 mm to 0.5 mm, means for containing the liquid cosmetic composition, means for supplying the liquid cosmetic composition to the nozzle, an electricity source, high voltage circuitry arranged so that, in use, liquid cosmetic composition sprayed in atomised form from the nozzle is electrically charged, and control means for selectively applying a high voltage.

An electrostatic spraying device comprising a nozzle, means for establishing a column of material to be sprayed within a passage leading to the nozzle outlet such that the leading surface of the column is spaced from the nozzle outlet, means for pneumatically ejecting said column or part thereof from the nozzle and means for applying high voltage to the material so that the spray formed by breaking up of the column on ejection from the nozzle are electrically charged. The column of material in the passage is preferably a discreet slug having a leading surface spaced from the nozzle outlet and a trailing surface to which air, gas or vapor under pressure can be applied to effect ejection of the slug from the nozzle.