Might make a big difference if you are exerting yourself, eg cycling. Discussion here from 2019 about heat exchanger masks seems relevant. They warm incoming a

Might make a big difference if you are exerting yourself, eg cycling. Discussion here from 2019 about heat exchanger masks seems relevant. They warm incoming air using the heat from outgoing breaths. https://news.ycombinator.com/item?id=39128311 https://news.ycombinator.com/item?id=39128311