In this article, a low-cost and pocket-sized setup for measuring CO[subscript 2] is presented. This setup is based on Arduinos, making it economic and open to modifications or improvements that satisfy other needs. It is composed of an Arduino board, a CO[subscript 2] sensor, an SD-card module, and a control panel. The device has been tested in three different experimental contexts that are typically used in primary and secondary science education: chemical reactions, plant photosynthesis and respiration, and gas diffusion. Results show major potential for the device, both for promoting students' model-based inquiry and for encouraging students to build their own devices and develop engineering practices. The other advantages of the proposal, compared with commercial data loggers, are also discussed.