Abstract: A method of controlling an oxygen concentrator having a first sieve bed operated over successive control periods according to a duty cycle for alternately pressurizing and flushing the first sieve bed and a second sieve bed operated over the successive control periods according to a reciprocal of the duty cycle is disclosed. The duty cycle and the reciprocal duty cycle are adjusted during every second one of the successive control periods to change the pressurizing relative to the flushing of the first sieve bed and to change the flushing relative to the pressurizing of the second sieve bed, for reducing concentration of oxygen produced. The duty cycle and the reciprocal duty cycle are adjusted during remaining control periods to change the flushing relative to the pressurizing of the first sieve bed and to change the pressurizing relative to the flushing of the second sieve bed, such that water vapor is purged from the first and second sieve beds after pressurizing thereof.

Abstract: A gas analysis apparatus using multiple orifices of preselected sizes to attain a calculated gas mixing ratio for diluting an oxygen sample to a concentration less than 95% prior to application to a limiting current oxygen sensor. The apparatus comprises a regulator for regulating the pressures of incoming flows of air and oxygen sample to be measured, a valve for allowing the concentration of the air sample to oxygen sample to be measured, and a system for calculating the air sample/oxygen sample mixing ratio based on the known air sample concentration and then, based on the known air concentration and calculated mixing ratio, calculating the unknown sample concentration from the output of the oxygen sensor.