“…However, even with these precautions, according to the period of the sport event and especially during long efforts, the PFCs may be totally excreted and undetectable in expired air. Moreover, excretion rates of PFCs are deeply linked to several parameters as their nature, the quantity injected, the size of the emulsion particles [23,24], the emulsifier [25,26], etc. All these variables could lead to important variations for the analysis of PFCs in expired air.…”