Cycling's governing body, the UCI, has officially banned the repeated inhalation of carbon monoxide "to protect the health of riders" after it was approved by its UCI Management Committee.
The ban will come into force from February 10, the UCI announced on Saturday after the UCI Management Committee met between January 31 and February 1 in Arras, south of Liévin, where the UCI Cyclo-cross World Championships are currently ongoing.
"The UCI takes a bold and necessary stance by banning the repeated use of carbon monoxide inhalation on medical grounds," said UCI President David Lappartient, who announced this ban would be the governing body's aim back in December.
"Our priority is to protect the health and safety of our athletes, and today’s decision is another significant step in this direction."
The use of carbon monoxide in cycling became a contentious point after the Escape Collective revealed that top teams Visma-Lease a Bike and UAE Team Emirates had used CO rebreathers to optimise training at altitude camps.
This particular use, however, has long been common in sports medicine for measuring total haemoglobin mass and blood volume in order to "examine the effects of endurance training and altitude exposure on oxygen carrying capacity."
Top GC riders Tadej Pogačar and Jonas Vingegaard later confirmed they had used CO for this purpose.
What the UCI are banning is a different method - repeated inhalation of the poisonous gas, which recent research suggests could be performance-enhancing and improve an athlete's aerobic capacity if done more frequently.
"[Carbon Monoxide's] repeated inhalation can result in acute and chronic health problems, for example, headaches, lethargy, nausea, dizziness, and confusion," read a statement from the UCI.
"Such symptoms can worsen at any time and develop into problems with heart rhythm, seizures, paralysis, and loss of consciousness."
The technique has not yet been banned by the World Anti-Doping Agency; however, the UCI has called for the international independent agency to take a position on the repeated use of CO in and out of competition.
From February 10, when the ban comes into place, the UCI will also tighten restrictions on the still-legal use of a rebreather for measuring haemoglobin mass. It will now be confined to a "medical facility", with only one CO inhalation permitted, and be under the supervision of a "medical professional experienced in the manipulation of this gas for medical reasons."
Any use of CO inhalation to measure an athlete's haemoglobin mass must also be recorded in their respective medical file.
