It was mentioned in another thread that there is some angst associated with using a chin strap and that would certainly be normal as it is just another piece of gear to drag us down. But it may also be because people are not using it correctly.
The chin strap does not need to be tight and should not be pulling your jaw into an unnatural position.
For purposes of PAP support (not snoring or other issues about which I know nothing) the chin strap is used to address PAP leakage through the mouth while you are trying to breath through your nose.
It is not for mask leakage.
It is not for those who cannot breath through their nose for some reason.
Mouth leaks are stopped by suctioning your tongue to the roof of your mouth. Suck your tongue up like you would if you were sucking on a lozenge or small piece of hard candy. Keep it back behind your upper teeth. Once you do this it will want to stay there. This should feel like a natural placement, do not suck it back toward your throat where it feels unnatural. When you do this placement correctly air will not leak. Some people don't need to do anything else.
However if your jaw tends to drop while sleeping it will drop too far it will pull the tongue down with it. This is where the strap is useful. It does not need to be tight or even snug. It just needs to prevent the jaw from dropping enough to dislodge the tongue. Once you place your tongue you can test this by letting your jaw drop and notice where it begins to pull the tongue. The second thing to consider is that for some strap styles, too loose means it will slide off your head. So you may need to tinker a bit.
The chin strap is NOT used to force your jaw or lips tightly closed. It is used to support your jaw in its natural position while you use your tongue to prevent the air passage out your mouth.
if you can't decide then you don't have enough data.
Great post MB. It goes a long way in explaining the function of the chin strap. I hope no one minds but I would like to add a little to this store of knowledge.
Having tried a number of chin straps before finding one that works for me, I am no expert but I have noticed a few things.
There seem to be primarily two different types of chin straps. One is the type that is intended to go over the end of the chin and has a cup type of arrangement for the chin. The other general type that I see is the wider strap that appears to be intended to go under the jaw and covers the whole underside of my jaw. This is the style that I found to work for me. I tried a number of the straps that go over the chin and they did not help me at all. They obviously help some people so if one type does not work for you try the other type.
The other significant differences seem to be how the strap is designed to remain on the head for the whole night. Some are a simple single strap and some have additional straps to aid in retention. I could not keep a single strap type on my head and so quickly figured out that I needed at least a second strap going around the back of my head to keep it on. Here again simple works for some people and some require more help for retention.
One other thing that I have noticed recently. Retired_Guy always used to say that a chin strap should encourage your lower jaw forward. I always wondered how that worked (still do) since the strap at best runs straight up and at worst runs diagonally toward the back of the head. Now that I have a chin strap that is working for me, I have awakened several times with my lower jaw positioned forward of it's normal position.
Just some observations that I hope may help someone along with MB's great post.
This is exactly what I needed to see considering I tend to breathe through my mouth during sleep. Thank you for the info!