A new ISO standard concerning the cleaning of sprayers (ISO DIS 22368) is on the way to be defined. It deals with both external and internal cleaning of the sprayers and aims at defining standardized procedures for the evaluation of the efficiency of the cleaning devices provided with the machines. In the ambit of the studies carried out to prepare this standard, several tests were made in order to assess the external contamination of boom sprayers and of orchard sprayers according to different operating parameters (type of nozzles, operating pressure, boom height, air flow rate). Concerning the boom sprayers, both conventional type and air-assisted type were tested (in this latter case also the influence of the air stream orientation was investigated), while orchard sprayers were tested using different types of nozzles and air flow rates. Results pointed out that the use of different operating parameters has a considerable influence on the external contamination of the equipment. On the basis of these first data it will be possible to provide indications: a) to sprayers manufacturers for the development of adequate devices for the external cleaning of sprayers as well as for an appropriate design of sprayers and components; b) to the users concerning the equipment adjustment suitable to reduce pesticide deposits on the machine.