The maker of the device being used by teams admits enhancing performance could be possible, albeit easily detectable.

“When you inhale carbon monoxide you reduce [the] oxygen content of blood, so all of a sudden the body [behaves] as if you are at high altitude,” says Carsten Lundby co-founder of rebreathing equipment manufacturer Detalo Health.

“If you inhale it once, it’s like being exposed to high altitude for a couple of hours – this will do nothing to your performance.

“If you inhale carbon monoxide four or five times a day over the ratio of a month, you will get more haemoglobin, but this would be a misuse of our device – this is not what it was intended for,” adds Lundby, who is also professor at the University of Lillehammer in Norway.

“And due to real-time surveillance of each machine, we can easily identify whether our devices would be misused.”

The UCI is not necessarily looking to snuff out cheating with a ban. It says it is seeking the ruling on grounds of safety, saying the practice still could be used in a “medical setting”.

But Lundby and teams are confused.

“At first I was happy to see the UCI taking a stance but then a bit baffled on the wording that these be allowed to be performed in a medical setting. I’m not aware of any medical settings where this has been done,” says Lundby.

“Colleagues and myself have been in touch with the UCI stating that 99% of measurements are not performed in a medical environment but by medical-trained personnel. I’m sure the wording will be changed.”