Abstract: Disclosed is an inventive valve assembly (24) for coupling a respirator jacket (26) to a household vacuum cleaner (28). The respirator jacket is used to assist a human user (22) in breathing. One embodiment includes a fixed first conduit (48) and an oscillating second conduit (44) which moves on a rocker arm (62) into and out of fluid communicating position with the first conduit. A cam assembly (72) having two arcuate cam surfaces (A1, B1) is adjustable to vary the duration during which the conduits are in fluid communication. Also adjustable is the frequency of oscillation of the second conduit. The duration and frequency are independently adjustable. Reference numerals used in this Abstract highlight the Detailed Description and Drawings, and do not limit the scope of the invention, which is much more broadly defined by the claims.