Abstract: Process for controlling the rate of gas extraction of a gas extractor for an enclosure of a cryogenic apparatus comprising a cryogenic fluid feed and an internal atmosphere, the apparatus being in contact with an ambient medium, comprising the steps of:measuring the content (m.sub.02) of the internal atmosphere of the enclosure in terms of a gas of the ambient medium;defining a target content (u.sub.02) for the measured content;calculating the rate of gas extraction (r.sub.c) of the extractor as a function of the measured content (m.sub.02) so as to maintain this content substantially equal to the target content (u.sub.02); andoperating the extractor on the basis of the calculated rate of gas extraction (r.sub.c).

Abstract: Device for protecting an ejection outlet of a burner mounted through a wall of a furnace, comprising a peripheral heat shield around the ejection outlet of the burner comprising a consumable structure comprising a refractory material and a mounting for heat shield comprising a mover which moves the heat shield relative to the wall of the furnace, between at least two positions which are spaced apart along the axis of the burner.