Controversial chapter finally closed: After UCI, WADA also bans carbon monoxide

Carbon monoxide was used in cycling to measure blood values. By inhaling the substance, athletes could optimize altitude training. A rebreather, as the device was called, was controversial: if used four to five times a day over a more extended period, it was said to enhance performance. Moreover, it was bad for your health. The UCI investigated it and banned its use in February.

“Carbon monoxide is a toxic, odorless gas that is often the cause of accidents in the home,” according to a statement from the cycling association. "Inhaled in low doses and under strict safety conditions, the gas is used in medicine as a tracer to measure the pulmonary diffusion of oxygen or the total hemoglobin mass. However, when inhaled repeatedly under non-medical conditions, it can cause side effects such as headaches, fatigue, nausea, vomiting, chest pain, breathing difficulties, and even unconsciousness."

The UCI believes that these health effects, combined with the complete lack of knowledge about the long-term effects of repeated inhalation of carbon monoxide, justify a ban on the use of this gas for medical purposes. "However, its use in a medical setting, by qualified medical personnel and within the strict context of assessing total hemoglobin mass, may remain authorized."

Since the UCI ban, teams such as Visma | Lease a Bike and UAE Team Emirates - XRG have no longer used the measurement method. Incidentally, these teams only used it to measure hemoglobin, not to improve performance. In 2026, however, the ban will come not only from the international cycling union but also from WADA. From next year, it will no longer be permitted for use, except in some instances.

“The non-diagnostic use of carbon monoxide has been added to the list of prohibited substances,” according to a statement from WADA. “The use of carbon monoxide for diagnostic purposes, such as total hemoglobin mass measurements or the determination of pulmonary diffusion capacity, is not prohibited.”