The pneuPAC Model 2-R pneumatic logic ventilator with a new air entrainment valve that offers the option of an FIO2 of 1.0 or 0.45 is described. Its robustness, portability, variable FIO2, choice of positive end expiratory pressure and pressure relief valves make it versatile and suitable for transporting critically ill patients, as well as for resuscitation use when adverse conditions may be encountered. Two new medical air compressors, one mains driven and the other battery powered, designed for use with the ventilator, are also described. The function of the ventilator with the new valve was assessed using a piped gas supply and then reassessed when powered by the compressors.