Abstract: A positive displacement piston flow meter for measuring air flow comprising a hollow flowtube, preferably arranged in a vertical orientation, having a movable piston disposed in the flowtube for movement between a starting position, preferably at the bottom end of the piston stroke, and an elevated position at the top end of the piston stroke. The piston is reciprocated by means of a pressure relief control valve assembly which controls the ascent and descent of the piston. The piston is physically connected to the pressure relief control valve assembly by means of a flexible string, which causes the piston to automatically close the valve assembly for automatic operation on reaching the bottom end of the piston stroke and to reverse direction.

Abstract: An air sampler constructed as an integrated unit which can be attached to the clothing of personnel operating in an area where the air must be sampled. The sampler includes a pump, a damper, a regulator, a filter for removing dust or dirt from the air being sampled, and collecting or processing means for the sampled air. The pump is driven by a motor provided with a control which maintains the flow of air through the sampler constant. The regulator is connected directly between the inlet and the outlet of the sampler. It includes a pair of chambers separated by a flexible diaphragm, one chamber connected to the outlet and the other to the inlet. For a pressure differential exceeding a predetermined magnitude between the outlet chamber and the inlet chamber, the diaphragm by its flexing opens a valve to permit air to flow from the outlet to the inlet. The filter is in a transparent container so that it can be seen and removed when it becomes excessively loaded with dirt.