11. The secondary demand valve can be a hybrid of a demand valve and a buoyancy compensator inflation valve. 12. It was not until December 1942 that the demand valve was developed to the form which gained widespread acceptance. 13. This route can not be closed and supplies the helmet demand valve and free flow valve under normal circumstances. 14. The demand valve could also provide oxygen at any flow rate required to a conscious patient in respiratory distress. 15. By providing a secondary demand valve the need to alternately breathe off the same mouthpiece when sharing air is eliminated. 16. Use of the demand valve resuscitator in Europe was limited by the lack of pressure relief valve or audible alarm for high pressure. 17. It does not have a demand valve or electronic parts, and in theory this would be fewer parts to suffer from failures. 18. The vast majority of demand valves are open circuit, which means that the exhaled gas is discharged into the surrounding environment and lost. 19. The bailout valve ( BOV ) is an open circuit demand valve built into a rebreather mouthpiece or other part of the breathing loop. 20. The Commeinhes demand valve was an adaptation of the Rouquayoul-Denayrouze mechanism, not as compact as was the Cousteau-Gagnan apparatus.
