Preventing humidification rainout/condensation FAQs | ResMed
Preventing humidification rainout/condensation
Patients and Families > Support > Humidifiers > Preventing humidification rainout/condensation FAQs

FAQs: How can I prevent humidifier rainout/condensation?

Humidification adds moisture to the air that you breathe and can make your CPAP, APAP or bilevel therapy more comfortable. But some people experience difficulties with humidification condensation, also known as 'rainout'. Find the answers to the most frequently asked questions about humidifier rainout here.

I can't use my humidifier sometimes because the hose fills up with water. Why does this happen? What can I do about it?

This water is condensation and is often called rainout. If your room is cold, the warmed, humidified air cools down when it comes into contact with the colder air in the room. When the air cools, the amount of humidity (water vapour) that it can hold is reduced, and this causes the humidity to 'rain out'.

The amount of water that air can carry varies with temperature: warmer air can carry more water, while cold air can carry less. As the temperature drops and the air becomes cooler (e.g., overnight), the air is less able to carry water, so water condenses and forms droplets.

There are several ways to deal with this situation:

  • Use ResMed’s Climate Control system with the ClimateLine or ClimateLineAir heated tube. It prevents rainout by maintaining constant temperature and humidity levels.
  • Turn your humidity level down.
  • Raise the temperature of your bedroom at night to reduce the difference between the room temperature and temperature of the humidified air. Cover the tube with a ResMed tubing wrap to keep the tube, and the air travelling through it, warm.

I've heard that wrapping the hose with fabric will help with rainout. Is this true?

Yes. Wrapping the hose can help to insulate your treatment air from the lower temperature of the room, which helps to reduce rainout. The ResMed tubing wrap provides warmth and greater comfort while increasing the amount of humidity at the mask by up to 20%.