<p>A steam distribution apparatus comprising: a heat exchanger header defining a chamber; steam distribution apparatus communicating with the heat exchanger chamber; a source of steam at a pressure higher than atmospheric; a heat exchanger having one end communicating with the source of steam and another end for communicating with the chamber and steam dispersion apparatus; and a valve means : operating the heat exchanger in an open-loop for supplying humidification steam to the steam distribution apparatus at atmosheric pressure and operating the heat exchanger in a closed-loop at the steam pressure higher than atmospheric for heating the heat exchanger chamber wherein condensate within the chamber or steam distribution apparatus can be converted back to humidification steam.</p>
