ResMed’s HumidAire 4i is engineered to deliver 30% more heated humidification than the H3i. The humidifier is an integrated unit for use with ResMed S8 and S8 II series CPAP machines. The H4i Water Chamber has also increased in capacity up to 390 ml of water. This chamber is not only dishwasher safe it is also openable. This Chamber should last the life of your machine.