Abstract: A method of measuring the containment efficiency of a biological safety cabinet comprises releasing an aerosol of identifiable droplets within the cabinet and then sampling ambient air in the proximity of the cabinet so as to determine if particles of said droplets have escaped from the cabinet. Apparatus for producing a suitable aerosol comprises an impeller rotatable about an upright axis, an electric motor for rotating the impeller at high speed, (e.g. 20,000 to 30,000 r.p.m.), a reservoir for potassium iodide aerosol solution disposed above the impeller, and a hypodermic needle for providing a controlled flow of aerosol solution from the reservoir to the impeller, whereby rotation of the impeller disperses particles of the aerosol solution.

Abstract: A support appliance, such as a bed, having an articulated head section is disclosed in which the head section is raisable pneumatically using a bellows and the appliance includes a pneumatic control valve which automatically feeds air to the bellows to compensate for air losses inadvertently occurring in the system and thereby maintains the head section in a predetermined raised attitude.