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H5i vs. H4i

Yes, this is normal operation for the H5i. There are a number of differences between the H5i and H4i humidifiers that cause this. These are as follows;
H4i H5i
Heater plate temperature is based solely on the dial setting and remains constant if the dial setting is not changed. The heater plate temperature changes to ensure a constant humidity level. Heater plate temperature depends on the ambient (room) conditions, the humidifier setting and the air flow.
The moisture output will vary for a given dial setting, depending on ambient conditions and air flow. The moisture output for any given humidifier setting does not change, irrespective of changes in ambient conditions or air flow.
The heater plate temperature is not software controlled. The heater plate temperature is software controlled. If no flow is detected then the plate will not heat.
Yes. The water level left after use doesn’t give the best indication of unit function. As the H5i provides constant moisture output, it only uses the amount of water needed to provide the required level of moisture. If set at the same Climate Control temperature throughout the year, the H5i will use significantly less water during summer than it will during the winter.
Yes. To confirm H5i function, complete the following steps;
  1. Disconnect ClimateLine tubing and remove the water tub.
  2. Place your hand on the heater plate to assess the temperature of the H5i heater plate while the S9 is not running. Do not place your hand on the heater plate if the H5i has been running in the 10 minutes prior to this test as it may still be hot.
  3. Set the humidifier output to 6.
  4. Place the unit in warm-up mode amd allow it to run for 1 minute.
  5. Place your hand above the heater plate (without touching it) to confirm an increase in heater plate temperature. Don’t place your hand directly on the heater plate as it will be hot.
  6. Press the dial for 3 seconds to enable cooling down mode.



Under certain use conditions it is possible for the S9 to incorrectly display a fault message regarding the ClimateLine tube. An incorrect fault message will occur only when a ClimateLine tube is being used and if the temperature inside the cuff attached to the mask exceeds 32°C (90°F). Typically this will only happen in warm room conditions, or if the ClimateLine tube cuff is placed underneath bed covers during therapy or left in direct sunlight during standby mode.

In order to confirm whether the ClimateLine tube is indeed faulty, briefly disconnect power from the device. If the fault message persists and is visible immediately after the S9 is powered up then the fault message is real and the ClimateLine tube should be replaced. In this case, therapy is not possible until the ClimateLine is replaced or the tubing is temporarily switched to the SlimLine.

If the fault message disappears then there is no fault with the tube. After allowing the tube cuff to cool below 32°C, removing power from the device will cancel the fault message and allow further use of the S9 system. But if during therapy mode the temperature inside the cuff again exceeds this temperature, the fault message will recur.

These operating conditions present no safety issue and it is not the intended operation for the S9 to display this fault message under these conditions. A simple software fix has been implemented in production to prevent this fault message being displayed.

The following advice actions can help to minimise the chance of this fault message recurring:

  • Ensure the humidifier tub is full at the start of therapy. Operating with little or no water will allow more heat to be transferred from the H5i heater plate to the tube and increase the chance of exceeding 32°C at the cuff.
  • Turn down the humidifier setting (in Manual mode) or ClimateLine setting (in Auto mode).
  • If the above actions do not satisfactorily resolve the issue, the device should be returned to ResMed.


Water in my hose

This condensation is 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 warm air becomes cooler (eg, overnight), it has less capacity to carry water, so water condenses and forms droplets.

There are several ways to deal with this situation.

  1. Use the S9 Climate Control system.
  2. Try turning your humidity level down.
  3. Raise the temperature of your bedroom at night to lessen the difference between the room temperature and the humidifier—make sure that your bedroom window is closed.
  4. Run the air tubing beneath your blankets to keep it warm. Alternatively, you can cover the tube with a ResMed Tubing Wrap or a tube sock. The goal is to keep the tube and its air warm.



The setting on your humidifier will set how much moisture you receive to alleviate your symptoms. The higher the setting, the more moisture. This is best checked first with your Clinician and User Guide.

If you start your setting for example at a midway point, and if your symptoms are not resolved, you may need to turn it to a higher setting. Continue in this manner until your symptoms are resolved. If you start to experience moisture in the tube, you need to turn it down, heat the room, use a ResMed Tubing Wrap or use the S9 Climate Control system.

If you are finding that you have nasal symptoms at other times of the year, then you should probably use your humidifier. The added humidification will probably increase the comfort of the air as it is more fully moisturized.

The amount of water needed varies from one humidifier to the next, from one patient to the next, and with the temperature and humidity of the bedroom.

Mouth breathing or mouth leak. can make you use more water from your heated humidifier.  All the escaped air through the mouth (which can vary from night to night), uses up the water more quickly.

A full face mask should not change the amount of water used each night. If you had a mouth leak before, you could have been losing lots of air and humidity through your mouth, in which case you should use less water now.

The CPAP should always be placed either at the same level or above the humidifier to reduce the risk of water entering the CPAP machine.

To further ensure water does not enter your CPAP machine, empty the water tub and disconnect the humidifier from your CPAP machine before transporting it.


The tubing supplied with CPAP machines can withstand far higher temperatures than the heat generated by the humidifier.

If you find the air dry and irritating, then you may want to turn your humidifier on 20 minutes prior to going to bed.

Humidification doesn't help with OSA or UARS, it does help with side effects caused by CPAP. If you are already on CPAP treatment and experiencing nasal dryness/symptoms, then humidification should help decrease the symptoms. The nasal symptoms are due to the increased flow of air through the nasal passages. Humidification adds moisture to the air breathed and helps the nasal passages cope with the increased flow of air.

The water should be changed for each use - even if you don't use it all in one night.

If you have a standard humidifier tub, it is recommended that you use distilled or deionized water. If you have a cleanable tub, tap water is fine for everyday use.

Do not use: bleach, alcohol, chlorine or ammonia-based solutions; moisturising, antibacterial or glycerine based soaps; and water softening and unapproved descaling agents.




It is recommended that you wash your water tub in warm water, using a mild detergent.

Rinse thoroughly with clean water and allow them to dry away from direct sunlight.


  • Inspect the water tub for wear and deterioration.
  • Replace the water tub if any component has cracked, become cloudy or pitted.
  • Clean white powder or deposits in the water tub by using a solution of one part household vinegar to ten parts water.



Because you can adjust the level of heat, heated humidification offers greater flexibility and reduces more severe symptoms. Both nasal pillows and masks are a viable option when using humidification; however, "rainout" (moisture caused by having the humidifier turned up too high) when using nasal pillows may become more of an issue as the moisture is directed into the nostrils.
Up to 40% of PAP users experience nasal congestion and dryness of the nose and throat. These symptoms can be severe enough to prevent patients from continuing their treatment. ResMed heated humidifiers add moisture and warmth to the air delivered by a CPAP or bilevel system. This reduces symptoms of dryness and congestion, improving patient comfort and compliance. Research also shows that nasal resistance can promote mouth breathing, which in turn leads to additional dryness. Heated humidification can prevent the large increase in nasal resistance that results in mouth breathing and leaks.




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