Proper aeration is necessary, in most cases, for normal development of plants grown in nutrient solutions. In many research institutions a central air compressor makes air pressure available in laboratories and greenhouses through a piping system. When an air compressor is not available, enough air pressure for the aeration of nutrient solutions or for similar biological work can be obtained with laboratory built equipment, utilizing the hydrostatic pressure of the water piping system. Riker and Riker (1) describe an apparatus which supplies continuous air pressure, obtained by connecting the exhaust tube of a water suction pump to a bottle or similar container fitted with the proper tubing for air and water outlets. The writers have built the equipment described by these authors and used it for the aeration of plant nutrient solutions. It was noticed, however, that the aerator worked well only when the hydrostatic pressure of the water going into the suction pump was strong and fairly constant. Under conditions of variable hydrostatic pressure it does not work satisfactorily and requires constant regulation. After experimenting with several modifications of similar apparatus, the writers arrived at a simple model that supplies intermittent air pressure and that can be used under almost any condition of hydrostatic pressure. The air pressure thus obtained is enough for the aeration of plant nutrient solutions and probably could be used for other types of work that require aeration.