This device was designed to study the gas exchange resulting from the respiration of small organisms (meal worms, snails ...) or resulting from photosynthesis for a plant.

It consists of two round bottom tubes connected by a glass capillary. On each tube a stop valve is arranged for controlling exchanges.
The first tube allows the introduction of the organism to study, the second acts as a barometer. The CO2 released is absorbed by a solution of potassium hydroxide which causes a change in the level of liquid in the capillary tube.