Apparatus and method for dispensing active materials.

A method of dispensing active materials, the method comprising emitting a first active material (A) for a first period of time; emitting the first active material (A) and a second active material (B) for a second time period, wherein the active materials (A, B) first and second alternately emitted during the second time period; and emitting the second active material (B) for third period of time in; characterized in that the active materials (A, B) first and second are emitted alternately during the second time period such that when a burst (11, 13) of one of the active materials (A) is emitted, starts a burst (12, 14) of the other of the active materials (B) before the end of the burst of one of the active materials (a).