U.S. triathlete Jarrod Shoemaker has a decision to make at the opening ceremony of the Olympics next month in Beijing: Should he strap on a mask?

Chinese officials insist the notorious Beijing air will be cleaner by August, making such contraptions unnecessary. Concerned about the pollution, the U.S. Olympic Committee is distributing a high-tech mask, developed in secrecy, to its more than 600 Olympians. If athletes deploy it, they risk insulting the hosts. Then there's the geek factor.

"I...