I have altitude issues and I go to Denver at least 1/year. A few years ago, a friend brought me 2 small oxygen cannisters that have a mouthpiece, and you can take inhales straight from the cannister. at the time, I was experiencing altitude sickness. I think I took about 10 huffs and within an hour started feeling better. I used throughout day-just periodically and the following days felt fine. I'm going to Denver and will definitely pack 2 in my suitcase. I bought mine off of amazon, but I believe they sell in some Denver grocery stores and maybe sporting goods stores?