American media outlet stirs up story about carbon monoxide, but Pogacar and Vingegaard see no harm in it

What exactly is it? "Escape Collective can reveal that multiple Tour de France teams are using the controversial and potentially dangerous practice of inhaling the deadly gas carbon monoxide to optimise their athletes’ altitude training," it reported. "At least three teams, including the Visma-Lease a Bike and UAE Team Emirates squads of top contenders Jonas Vingegaard and Tadej Pogacar, and Israel-Premier Tech have access to an expensive device called a carbon monoxide rebreather."

There are two applications available: one for measurement and one for inhalation, but all teams assert that they only use it as a measuring tool. Although it could be used for the more controversial inhalation, there is definitely no evidence of this so far. "We have been working with Norwegian Bent Rønnestad for a few years now to do measurement at the beginning and end of altitude camps," Mathieu Heijboer of Visma | Lease a Bike told Escape Collective.

Some team officials were confronted with the 'exclusive' story. "It's blown out of proportion," Visma | Lease a Bike sports director Merijn Zeeman told HLN. "It's searching for trouble where there is none. It's simply the most common method to measure hemoglobin mass, a method that has been in use for years."

"There have been some scientific studies, but I have not heard that it really works effectively," continued the Dutchman. "We are very clear and transparent as a team: we do not use it in that way and haven't even considered using it like that. Should it prove to be an effective method to produce extra red blood cells, hopefully, WADA will intervene quickly."

Team leader Jonas Vingegaard had previously said the same. "We just use it to know how much hemoglobin you have in your blood. There's nothing suspicious about it or anything," he said on the rest day, dismissing the story as speculation.

Tadej Pogacar, as the wearer of the yellow jersey, was also asked about the matter. "Is it the exhaust of a car? I don’t know anything about that, so I can’t comment," he stated on Tuesday. A day later, he revisited the question during his press conference. "I didn’t understand the question earlier. It's a test we do to see how you react to a high-altitude camp. You breathe in and out with a balloon. This is repeated after two weeks to see the effect. I never did the second time because the woman didn’t show up. But it's nothing unusual," quoted De Telegraaf.