The invention relates to an active body, comprising an active material (1) for the pyrotechnic production of smoke or for providing a pyrotechnic decoy target and a sheath (2) for containing the active material (1) as well as optionally an ignition means, wherein there is at least one gap (3) between the active material (1) and the sheath (2), wherein the nature of the gap (3) is such that it extends over at least 75% of an entire surface of the active material (1) and a flame can propagate through the entire gap (3) between the active material (1) and the sheath (2), wherein the nature of the sheath (2) is such that it only breaks open under a pressure building up in the sheath (2) as a result of a reaction of the active material (1) and - if present - of the ignition means after the flame has propagated through the entire gap (3). Fig. 1 +2 1 >-3 Fig. 1
