This European Standard deals only with the significant hazards of machines for surface cleaning and pre-treatment (in the following called "cleaning machines") of industrial items using water based cleaning liquids in the mode of suspension, solution or dispersion of compounds or substances in water applied by immersion and/or spraying in one or more stages.This European Standard applies in combination with EN 12921-1. Both parts together cover all significant hazards relevant for cleaning machines for industrial items using liquids or vapours, when they are used as intended and under the conditions foreseen by the manufacturer (see clause 4). The specific requirements specified in this standard take precedence over the respective requirements in EN 12921-1. This standard should be applied together with EN 12921-3 in case of release of flammable vapours from water based cleaning liquids. This European Standard applies together with EN 12921-3 and prEN 12921-4 in case of use of water based cleaning liquids of which evaporating can lead to hazards caused by explosive atmospheres. Water based cleaning liquids containing a quantity of halogenated solvents exceeding 2 % of the volume are considered hazardous with respect to the creation of a potentially explosive atmosphere.This European Standard does not apply to machinery and related equipment excluded from the scope of EN 12921-1. This European Standard does not apply to cleaning machines for industrial items using water based cleaning liquids which are manufactured before the publication of this standard by CEN.