In the opinion of the writer the bald name “ Pressurisation ” gives a crude and misleading picture of the developments which are now in hand and both he and the organisation to which he belongs, prefer to speak of “ Cabin Air Control,” as this name gives a clearer picture of the scope of the developments which are the subject of this paper.

At the outbreak of the war the evolution of passenger-carrying aircraft had reached a stage where a great deal of attention was desirable for the comfort of passengers and, in those passenger-carrying aircraft which have subsequently gone into service, it is fair to describe Pressurisation as a development directed almost entirely towards the greater comfort of the occupants.

The recent war has provided a great deal of experience in the operation of aircraft and ground equipment under a variety of conditions. This paper is an attempt to condense and correlate some of the points noted into a logical sequence. It is not based on statistics and is more in the nature of a selection of problems and impressions about them. Possibly this is an advantage, as it seems doubtful if many logical conclusions could be drawn from a set of completely comprehensive observations, even if these were available.