Abstract: In a chemical process plant or the like, of the type having a gas turbine driven compressor and a fired heater for heating the process medium, and of the type which hitherto used the exhaust (GTE) of one or more gas turbines as an oxidizing medium input for oxidizing the fuel in the radiant section of the fired heater, the GTE is instead now diverted from the radiant section to a heat exchanger and air at substantially atmospheric pressure and ambient temperature is forced through the heat exchanger by a fan so as to be heated by the heat energy derived from the GTE and is then fed to the said oxidizing medium input of the heater radiant section. The GTE which has passed through the heat exchanger is exhausted to atmosphere.

Abstract: An improved protective face mask periphery includes an inturn having a flat ortion extending inwardly of an inner surface of the face mask, and a curved bubble portion which is concave with respect to the inner surface of the face mask and which curves outwardly into engagement with the wearer's face. The face mask periphery thus forms a good seal with the wearer's face while at the same time being comfortable to wear.