A pen for washing a small child, intended for use in a shower or bathtub. An air supply system 20 for supplying combustion air to cylinder 12 comprises first and second air intake systems 30, 50, each including an air passage 33, 53 and a valve 40, 60 controlling air passage through their respective port 31, 51. 004 to 20% by weight of a biocide which said composition is in the form of fine particles of an aqueous gel containing the water, gelling agent and the biocide, the surfaces of which fine particles are coated with a coating of the finely particulate hydrophobic silica. Such directly identified compounds can be utilized, most preferably, in pharmaceutical compositions.