An inexpensive and demountable walk-in incubator.

times after the incubator doors had been opened and closed (45 minutes to 45 hours), and in the centre of the highest and lowest shelf positions. The CO2 concentration varied between 31 % and 7-2 % and in practice a rate of between 20 and 60 ml per minute was found to support the growth of carbon dioxide requiring organisms such as newly isolated strains of N. gonorrhoeae and Br. abortus (including biotype 2). The cost of the modification totalled £35 and the running costs are approximately lOp per week. Referece Lloyd, B. B. (1958). Development ofHaldane's gas analysis apparatus. In many areas of scientific work there are advantages in the use of walk-in incubators or 'hot rooms'. Those models which are available commercially are, however, expensive and, in the event of the rearrangement of the laboratory in which they are housed are extremely cumbersome to disassemble. During the development of the virus laboratory in the Department of Microbiology at King's College Hospital Medical School considerations such as these led us to design an inexpensive and demountable hot room. Structure of Hot Room The room is 2-4 m x 1-75 m, with a sloping roof, the height of which ranges from 2 25 m to 2-6 m; its volume is 10 5 i3. The roofslopes for ease ofdusting and to avoid thecollection ofdebriswhich oftenoccurs on low-level flat roofs. The walls and roof consist of expanded polystyrene bonded to hardboard and are of about 5 cm thickness. They slot into and are supported by a framework of anodized extruded aluminium girders of a type specially prepared for and supplied by Murr Internal Constructions Ltd. These girders are H-shaped in cross section and the depth of the slot on each side is about 1-25 cm. The H shape is modified at corners and at roof-wall junctions. A single standard-size door is fitted; this fits into an aluminium frame which has a 7*5 mm x 3 mm foam rubber sealing strip inserted, providing a tight fit at top and sides. At floor level we have found no need for a draught excluder (but one could easily be installed) and we consider that it would be dangerously easy to trip over a raised floor 'rebate'. Heating Equipment The source of heat is a 3 kw fan heater (type General Electrical Company H6448D) which is mounted in an upper corner of the room and set …