A simple lever control enables the subject to be connected either to atmosphere or to the float for recording. A container for soda-lime crystals is fitted which can be used to absorb carbon dioxide. The spirometer is designed to offer minimum resistance to air flow. This means greater comfort for the subject and more realistic results. The tank is one piece stainless steel pressing housed in a durable painted outer case. Ther float is contructed from lightweight plastic. The float is calibrated 0 to 7 x 0.5 litres and has a metal counterpoise. The pen arm corresponds to approximately 0.5 litres. The two corrugated breathing hoses 0.8m long are provided with two mouth pieces and a nose clip. Instructions supplied.