Obviously you can’t tuck your nose and mouth (unlike the rest of your face) in your sleeping bag otherwise it will become saturated from your breath and no longer keep you as warm. Until now I just put up with it. Recently though I discovered this wonderful product which when worn over your nose and mouth of a night warms the air (and your nose) so giving you a much more pleasant night. The Buff: It can also be worn in a bewildering array of other combinations. It weighs only 37.5 grams. Stow one in your pack. You will not regret it. It is made of 100% pure merino wool. As you can see, it improves my appearance no end! This is a good camo colour too! http://buffusa.com/ & https://www.buffwear.com/ The Buff comes in a lighter fabric for summer wear.