in which Xf = fluorine concentration in % by volume/100.
Mixtures of fluorine and inert gases with a fluorine concentration below 35% by volume may be filled in pressure receptacles up to a maximum allowable working pressure for which the partial pressure of fluorine does not exceed 31 bar (abs.), additionally taking the coefficient of nitrogen equivalency in accordance with ISO 10156:2017 into account when calculating the partial pressure.
in which Xf = fluorine concentration in % by volume/100.
Kk = coefficient of equivalency of an inert gas relative to nitrogen (coefficient of nitrogen equivalency)
Xk = inert gas concentration in % by volume/100
However, the working pressure for mixtures of fluorine and inert gases shall not exceed 200 bar. The minimum test pressure of pressure receptacles for mixtures of fluorine and inert gases equals 1.5 times the working pressure or 200 bar, with the greater value to be applied.
49 C.F.R. §173.302b