Resmed S9 Heater

OK, here is what I have done for tonight. Climate Control is set at patient. I have set the hose to 70. Now is that degrees or percent humidity? Also my humidifier is set at 2. I always assumed that was heat increments, the higher the number the hotter the water got and hence warmer in the mask. Is that correct? No the amount of humidity. I get confused.

So with the humidifier at 2 and the hose at 70, the climate hose will keep it at about 70 percent humidity based on room temp and humidity? Do have that right?

One more question. It said to push down the control knob to activate the humidifier. Doesn't the humidifier automatically start when I turn on the machine and start breathing. I thought the control knob was used to preheat not activate?

jrfoster wrote:OK, here is what I have done for tonight. Climate Control is set at patient. I have set the hose to 70. Now is that degrees or percent humidity?

The 70 is degrees---as in 70 degrees Farenheit.

Also my humidifier is set at 2. I always assumed that was heat increments, the higher the number the hotter the water got and hence warmer in the mask. Is that correct? No the amount of humidity. I get confused.

The answer is here is both yes and no.

Technically the humidifier setting does control the amount of heat provided to warm the water. And the warmer the water and the air inside the humidifier is, the more water evaporates into the air, and hence the more humidity is put into the air inside the tube. Hence, the higher the humidifier setting, the more humidity is added to the air inside the tube.

As a side effect of heated humidification, however, the air inside the tube is also slightly warmed, but much of that additional heat is lost over the length of the hose. When too much heat is lost or when the tube itself is cold (because the bedroom air is cold) that additional humidity can start condensing out of the air inside the tube and you get water droplets (aka "rainout") in the hose and mask. And that's why some folks find a heated hose useful. The heated hose heats the air inside the hose and keeps it nice and warm. And that in turn minimizes the rainout problems.

So with the humidifier at 2 and the hose at 70, the climate hose will keep it at about 70 percent humidity based on room temp and humidity? Do have that right?

No. You've still got it backwards.

When the hose set at 70, the ClimateLine hose will keep the air in the hose at 70 degrees Farenheit all along the entire length of the hose. So the air you are breathing in the mask will be about 70 degree Fairenheit regardless of how cold your bedroom gets during the night.

When the humidifier is set at 2, the warmer plate will provide a moderate amount of heat. This will encourage a modest amount of evaporation of water from the humidifier tank into the air that is blowing across the water in the tank. This process will also add a modest amount of heat to the air. But the exact temperature and the the exact relative humidity of the air entering the tube at the humidifier end of the hose will depend on the room temperature and the relative humidity of the air in the room. In other words, both the temperature and the relative humidity of the air entering the tube will vary from night to night based on the ambient conditions in your bedroom. That's because the machine is blowing room air across the warm water in the humidifier tank. In an unheated hose that slightly warmed and humidified air will cool as it is transported to your mask. And if the air cools too much, the water vapor will start to condense and you get rainout.


So when you have the humidifier set at 2 AND the ClimateLine set to 70 degrees, this is what will happen:

The blower unit sucks in (cold) room temperature air that varies in its relative humidity from night to night. The blower unit sends this air into the humidifier where it is blown over the modestly warm water. Some of water evaporates into the room temperature air and is now somewhat more humid than the room air itself. Because the humidifier is set to 2, the water is only moderately heated and so only a moderate amount of water is evaporated into the air. So at the point where the air leaves the humidifier and enters the ClimateLine hose it is a bit warmer than room temperature and it has a noticeable, but moderate, amount additional water vapor in it.

The humidified air then enters the ClimateLine hose. If the temperature of that air is below 70 degrees, the heating coils in the tube begin heating the air. And they continue heating the air until it reaches a temperature of 70 degrees. And because the heating coils run the full length of the hose, they continue to keep the air at 70 degrees for the full length of the hose. So the ClimateLine hose keeps the air inside the tube warm, and that reduces the chances of rainout.

The end result is that you will be breathing 70 degree air with a modest amount of additional humidity beyond the humidity that is already in your bedroom's air.

Thank you so much for that detailed explanation. It was MUCH easier when I did not use any heat and simply let the air pass over the water.
Life was much simpler then. Thanks for putting up with my lack of knowledge!

jrfoster wrote:One more question. It said to push down the control knob to activate the humidifier. Doesn't the humidifier automatically start when I turn on the machine and start breathing. I thought the control knob was used to preheat not activate?

I have to admit that it's been so long since I used an S9 that I don't know the answer to this question. But I believe that to pre-heat the humidifier you push the control knob down for 3 seconds. I believe when you first start the machine, the humidifier icon comes on and it will be set to your last setting. If you want to change it, you turn the knob until the desired setting shows and then you click to confirm. This allows you to change the humidity setting while the machine is on.