Humidifier “Rainout” FAQs | ResMed

Preventing humidification condensation

Are you experiencing difficulties with humidification condensation (also known as "rainout")? Find the answers to the most frequently asked questions about humidifier condensation here.

Q. I can't use my humidifier some nights because my hose fills up with water. Why does this happen, and what can I do about it?

A. This is known as condensation and is also called "rainout." If your room is cold, the warmed, humidified air hits the colder room temperature and cools. When air cools, the amount of humidity (water vapour) that it can hold is reduced, which causes the humidity to "rain out."

The amount of water 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), it has less capacity to carry water, so water condenses and forms droplets.

There are several ways to deal with this situation:

  • Use the ClimateLineAirTM heated tube to enable constant temperature and humidity control.
  • Try turning your humidity level down.
  • Raise the temperature of your bedroom at night to reduce the difference between the room temperature and the humidifier.
  • Run the air tubing beneath your blankets to keep it warm. Alternatively, you can cover the tube with a ResMed tubing wrap or even a tube sock. The goal is to keep the tube (and the air traveling through it) warm.

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

A. Yes. Wrapping the hose can help to insulate your treatment air from the lower temperature of the room, reducing "rainout." The ResMed tubing wrap provides warmth and greater comfort while increasing the amount of humidity at the mask. 

Do you have a question about humidification "rainout" that isn't addressed here? Talk to your ResMed accredited outlet

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