Abstract: An apparatus for decomposing injurious substances to form non-injurious substances comprising a first reaction vessel, an injurious substance inlet connected to the first reaction vessel for supplying an injurious substance containing only one of an oxygen or hydrogen donor substance, and at least one further reaction vessel connected to the first reaction vessel. A mixing vessel connected to the at least one further reaction vessel is provided with the first reaction vessel, the further reaction vessel and the mixing vessel containing an aqueous solution of sodium carbonate. Conduits may be provided between the first reaction vessel, further reaction vessel and mixing vessel, permitting circulation of the aqueous sodium carbonate solution. A feeding device is connected between the mixing vessel and the first reaction vessel for feeding the aqueous sodium carbonate solution therebetween and into association with the injurious substances supplied to the first reaction vessel.