Abstract: An improved air-to-air, heat-and-moisture exchanger is described which facilitates the simultaneous transfer of both heat and water vapor between two streams of air while greatly inhibiting the transfer of pollutant gases. A rigid encasement supports a stack of flat, thin-film composite membranes that are held in parallel, spaced-apart relation, thereby forming a box-shaped exchanger. The membranes are synthesized by interfacial polymerization, a process whereby a thin, non-porous film may be uniformly deposited onto a porous substrate material. The thin film is hydrophilic so as to provide high water vapor flux together with excellent selectivity against the transfer of other gases and vapors. The substrate provides mechanical support.

Abstract: A radiation level measuring system having a Geiger-Muller gas ionizing tube as a detector. The inherent dead-time of the Geiger-Muller tube that follows a discharge pulse is compensated by the pulse counting electronic measuring circuit. A signal pulse of varying duration is formed from the detector output pulses in a manner that corrects for this dead-time. Measurement of this generated signal pulse duration give the actual radiation level that would be measured if the detector dead-time did not exist.