The antimicrobial activity of acidified sodium chlorite is attributed to the oxidative effect of chlorous acid, which is derived from the conversion of chlorite ion into its acid form under acidic conditions. The reactions happen instantly on mixing the sodium chlorite with an acid (e.g. citric or phosphoric acid) and therefore the antibacterial solution needs to be prepared shortly before spraying – the effective shelf-life is less than one hour. Grayson Australia has developed a system which mixes the chemicals immediately before application to maximise the oxidising power of the solution.