Low flow active antipollution systems

Summary The performance of two low‐flow antipollution systems has been assessed by making measurements of the nitrous oxide pollution levels with four automatic ventilators. The effectiveness of the antipollution system is dependent on the volume of gas discharged, the peak expiratory flow, the airway pressure and to a lesser extent the ventilator settings. Both systems coped adequately with the clinical conditions where inflation pressures were below 4 k Pa for two ventilators. Only one system coped with these conditions for the third ventilator. The fourth ventilator, which discharged driving gas to the respired volume, was not adequately scavenged.