To meet this need, we introduce a low-cost, open-source environmental chamber. Commercial environmental chambers that control temperature and humidity can cost over US $10,000, and fully integrated solar device stability testing systems can cost up to US $60,000. Our chambers range from US $2,000-$7,500 depending on configuration, and offer environmental control as well as in-situ monitoring. Although the design principles of the chamber are broadly applicable, we designed the chamber specifically to test halide perovskites, a class of functional materials with nascent applications including photovoltaic absorbers, light-emitting devices, and X-ray detectors, among others , . Commercialization of the aforementioned devices is often limited by poor environmental stability under operating conditions - . This has led to diverse efforts to modify perovskite alloy composition and device architecture , with the aim of improving environmental stability and widening accessibility by reducing price. The extent and mechanism by which newly synthesized alloys and devices degrade under environmental conditions is a subject for study - .