The World Anti-Doping Agency banned the inhalation of xenon and argon gases, stating that they could enhance the performance of athletes, Agence France Press reported today.

Russian athletes were reported to have used xenon at Olympic Games at Athens in 2004 through Sochi in 2014. WADA contends that inhaling the gas increases the production of the hormone erythropoietin, which boosts production of red blood cells which transport oxygen to the muscles and increase athletic performance.

WADA also placed the substances on its prohibited list.

“The message to any athlete is loaded and clear, it’s going on to the banned list,” said WADA President Craig Reedie after the agency’s two day executive committee board meeting. “So, if in doubt, do not.”

The ban will go into effect after a 90-day delay to allow national anti-doping organizations to implement the change.

Russian athletes won the gold and all medals count at the Sochi Winter Olympics. According to AFP, the Russian Defense Ministry set out guidelines in 2010 for the administration of xenon gas to athletes.

Despite the lack of tests for xenon in an athlete's system at the moment, unexplained discrepancies in the athlete's biological passport suggesting usage of the product will be punished.