A source of gaseous, gas borne or droplet substance having: an inner pressurised container (1), a substance-release valve (2) device sealed across an end of the container (1), a spout (4) displaceable inwards of the container (1) against a spring of the valve (2) device for substance release; the source also includes: an outer enclosure enclosing the inner container along its length (12), at least partially its end (14) remote from the spout (4) and partially at its spout end (19), the outer enclosure ADN the inner container (1) being arranged to react force for displacement of the spout (4) on substance release; a counter (20) accommodated within the outer enclosure for counting substance release displacements of the spout (4); and a window (22) in the outer enclosure for viewing the count of the counter (20).