Abstract: Apparatus for forcing smoke produced by a smoke bomb into a cavity to test for leaks therein. The apparatus includes a housing for receipt of an ignitable smoke bomb to produce smoke therein, a blower and an engine to operate the blower. The blower includes a housing having an inlet, an outlet and a wire mesh screen barrier interposed therebetween. The smoke bomb housing is arranged to support the smoke bomb therein between the inlet and the wire mesh barrier. The outlet of the blower housing is disposed over the cavity and in communication therewith. In operation the blower draws air from the ambient atmosphere into the smoke bomb housing and about the ignited bomb. The cloud of smoke in the housing is drawn through the wire mesh screen, into the blower housing from when it is forced into the cavity. The wire mesh screen acts to arrest any sparks or flame produced by the ignition of the smoke bomb from gaining ingress into the blower housing and hence the communicating cavity.