I read this story in approximately 1979 (plus or minus a year); I found it in an anthology when I was systematically reading my way through all the SF in my library's YA section. Note that the book may have been much older; at the same time I read "A Treasury of Great Science Fiction" (both volumes), and those were published in 1959/60.
I'm 95% sure that the story takes place on Mars. A young man or youth, because of some accident or misfortune, (perhaps his vehicle crashed) is stranded alone and forced to try to walk to safety. It is part of the story that he is not as strong as most people; not that he is disabled, just that he is not as strong or as fast. It becomes important because his walk is one that a "normal" person would have been able to make, but he isn't able to move fast enough to get to safety before his air runs out.
He runs out of air, and rather than suffocate in his suit, he opens his helmet. And it turns out that he can breathe the atmosphere.