Abstract: Inland waters are important sources of greenhouse gases (GHG). The accurate quantification of fluxes is fundamental to assessing their roles in the global GHG cycle. The flux chamber method is the most widely used technique for measuring GHG fluxes in inland waters. Based on whether external air is introduced to maintain stable CO₂ concentrations inside the chamber during measurements, flux chambers can be categorized into two types: closed path (non-steady-state) chamber and opened path (steady-state) chamber. We reviewed the basic principles, practical applications, and respective advantages and limitations of those two types. The closed path chamber method is characterized by flexible deployment and simple operation, but it may disturb the micrometeorological conditions within the chamber. In contrast, the opened path chamber method maintains consistent environmental conditions between the chamber interior and the ambient atmosphere, but it imposes higher requirements on the precision of gas analyzers and the stability of control systems. Moreover, we discussed the uncertainties in flux measurements arising from factors such as chamber design (size and shape), observation duration, and gas transfer velocity. We further summarized key operational considerations, including chamber airtightness, pressure equili-brium, gas mixing conditions, and the measurement of gas mixing ratios. Finally, we outlined future directions and application prospects of the flux chamber method in inland water GHG research, aiming to provide a reference for method selection and technological advancement in this field.

Key words: chamber method, inland aquatic system, greenhouse gas flux, uncertainty