Sleep Apnoea Articles

CPAP Humidification and Rain Out

CPAP Humidification solutions from ResMed

Many obstructive sleep apnoea patients using CPAP devices experience nasal congestion and dryness of the nose and throat and this can compromise acceptance of treatment. With the flow of air from a CPAP machine already an irritant, lack of moisture in the air can cause nasal passages to dry and may induce bleeding, swelling, sneezing, snoring and congestion. In these situations the addition of CPAP humidification can reduce these problems.

Heated humidification offers greater flexibility and reduces more severe symptoms.

There are two categories of humidification – warm and cold. Cold or “passover” humidification was the first type of humidification therapy for CPAP. Cold pass over is a water chamber that allows air from the CPAP to “pass over” the water before entering the CPAP tube thereby creating humidified air. Although this set up is effective for CPAP users with low pressure settings and those living in a warm climate, it is not optimal as it can become too cold to tolerate and does not provide the most efficient humidification.

A heated humidifier adds moisture and warmth to the air delivered by the CPAP device. Because you can adjust the level of heat, heated humidification offers greater flexibility and reduces more severe symptoms and increases comfort of the treatment by the user. With increased comfort the user is likely to increase compliance and the ability to use the treatment for longer periods.

In the summer months, some are unfortunate to suffer symptoms of hayfever, a runny streaming nose, often alternating with congestion can be exacerbated by the CPAP treatment. In these cases, heated humidification can also help to relieve nasal irritation and aid continued use of treatment.

One of the problems that can sometimes occur with heated humidification is ‘rainout. In cold weather, as the warmed moistened air moves down the hose, it is cooled and can hold less water: as a result it condenses in the tube and mask. This is known as ‘rainout which can cause gurgling noises in the tube and water condensation on the face.
There are several ways to help to lessen the problem of ‘rainout and the following may help:

  • Always have the device and humidifier positioned lower than the bed
  • Close the bedroom window, turn the humidifier down or raise the temperature in the bedroom at night, to lessen the difference between the room temperature and the hose
  • Tuck the tube under the bedclothes to keep it warm
  • Insulate the hose by covering it with a tubing wrap. Custom made ones can be purchased from ResMed or alternatively you can make your own by wrapping a towel, scarf, bubble wrap or aluminium foil around the tube

ResMed has humidification solutions for both the AirSense 10 AutoSet™ CPAP devices and for the earlier S9 CPAP device.


CPAP Humidification ResMed

A heated tube that delivers air at consistent, comfortable temperature and humidity levels. A key component of ResMed’s Climate Control humidification solution for S9TM devices.

ClimateLine Air™

ResMed Humidification Solutions
ClimateLine Air

A heated tube that delivers air at consistent, comfortable temperature and humidity levels. A key component of ResMed’s Climate Control humidification solution for AirSense 10 AutoSet and AirCurve 10™ devices.


ResMed Humidification Solutions

An advanced heated humidifier that’s simple to use and highly effective at maintaining the optimal humidity level for a more comfortable therapy. When used with the ClimateLineAir heated tube, it warms the air at a consistent, comfortable temperature avoiding any rainout. Offers relief from dryness, congestion and condensation. Compatible with all AirSense™ 10 and AirCurve™ 10 therapy devices.

For more information why not speak to one of the ResMed UK team on 0800 917 7071 – it may be time to book an Annual Review. Or you can email us at

6 thoughts on “CPAP Humidification and Rain Out

  1. Hi

    I currently have AirSense 10 AutoSet, along with ClimateLine Air and HumidAir.

    The question that I have is, when I use the ClimateLine Air, is it supposed to only heat up for less than 5 minutes ? I was under the impression that the ClimateLine Air was to stay heated throughout until the AirSense was turned off ?

    If it is to stay heated throughout the night then I’ll be happy to return back to my provided for either repair or a replacement.

    Vinod Patel

    1. Hi Vinod, please accept my apologies for the delay in responding. We have have had technical issue with the comments function on the site, but it is now fixed. I have spoken to one of the ResMed UK team and they gave the following answer:”The ClimateLine Air should gently remain heated through the night to help prevent the build of rainout (condensation droplets) which can develop as a result of warm humidified air running through the tube at night. It is normal to not feel the tube getting warm so many do think the tube is not heating when in fact it is. Therefore if you are not getting any rainout in the tube this would indicate it is working as expected. Also, if the tube is not working an error message will usually display on the AirSense”. If you’re still unsure, then please call one of the ResMed UK team on 0800 917 7071.

  2. I’m having a issue with my ResMed , I am using the auto feature on all settings as prescribed by the company that sold my machine. I did have a bad “rain out ” instance on my machine that I felt like I could have drowned in my sleep . Must have been 1/2 a cup of water in my tube. The machine was replaced right away by the company.
    The problems I am having now is my nose canal is now super sensitive and always itchy . Like my all my sinuses are going nuts for the last month. Yes I’m using the right distilled water . It seems like I’m very dehydrated at night and always wakes me up blowing major air through my very now dry canals . Not sure what is up, but last night I said I’m not using the machine , and the morning the flew Linda symptoms were not as bad. I’m linking the problems I’m getting to this machine. At the beginning it seemed good, but now after 6 months of use, I’m not having much fun at all. My sleeps are getting worse not better.

    1. Hello Nick, we’re sorry to hear of the issues with your treatment. So we can offer the best possible advice for you, it would be helpful to know exactly which model/make of device and mask you are using. Can you confirm this please?

    1. Within the UK we advise patients that using plain tap water is perfectly safe and acceptable, so long as any unused water is emptied in the morning and fresh water added again at bedtime. If you live in a hard water area this may result in lime scale deposits building up, so it is important you clean the humidification chamber regularly. We recommend avoiding descaling agents which can affect the seals and instead using a solution of one part clear white vinegar to ten parts water, leaving to soak for 20 minutes then rinsing thoroughly. We hope this helps.

Leave a Reply

Your email address will not be published. Required fields are marked *