The World Anti-Doping Agency has decided it won't ban hypoxic chambers until further studies can determine their health implications.

Hypoxic or hyperbaric tents and chambers are used by many athletes to create high-altitude conditions and boost oxygen-rich red blood cell counts.

On Saturday, WADA ruled the chambers enhance performance and violate "the spirit of sport," but chose not to add them to the list of banned substances and methods for 2007.

"It doesn't mean we approve it," said Dick Pound,WADA head and Canadian IOC delegate.

Hypoxic tents came to national attention in 2003 when Canadian cyclist Genevieve Jeanson blamed the use of the tents for a failed doping test, which showed an unusually high red blood cell count.

"I intend to review my use of an oxygen tent, based on appropriate professional advice," she said in 2004. "I've used the tent for four years and I've come to believe that it does me good."

Pound said Saturday he wants the IOC to look into the health effects of using the tents to ensure they are safe for athletes.

WADA's scientific director, Olivier Rabin, said side-effects of using the chambers could include altitude-sickness, sleep disturbance and a possibly adverse effect of the immune system.

Pound also said he was pleased by the decision by former members of Lance Armstrong's U.S. Postal Service cycling team to admit they used the performance-enhancing drug EPO before the 1999 Tour de France.

"I hope [such honesty] continues and we certainly encourage it," he said.

Pound has been a vocal critic of Armstrong and in June dismissed a report clearing the seven-time Tour de France winner of doping allegations. Armstrong later sent the IOC a letter asking for Pound to be "expelled" from the organization.

With files from the Associated Press