I have seen a few guys come into the gym wearing these masks. Personally, they reminded me of a nanny we had hired years ago who insisted on wearing a face mask for hours at a time. I think the result of some nasty looking chapped lips far out weighed the benefits of wearing that mask…..our house wasn’t that dusty thank you very much…. Anyway, this new “training tool” is called an elevation training mask which is supposed to mimic the training effects of training at high altitude.
That type of training, when done at altitudes of 6000-10,000 feet above sea level is known to boost the bodies levels of the hormone called erythropoietin (EPO) which stimulates the body to produce oxygen carrying red blood cells. Kind of like legal blood doping. The overall lasting effect of this condition, when coming back down to sea level, is only a few days but these masks are being marketed for being able to produce the same or similar effect all the time.
So I did some research and came across an article by a pretty reputable guy, Doug Kechijian. I encourage you to give it a read before you decide to invest over $100 USD for yourself or your kid. You can find the article here: http://www.resilientperformancept.com/blog/elevation-training-masks-an-analysis