Technical Abstract: Emissions of many trace gases from the Earth’s surface to the atmosphere have a profound impact on the air quality we breathe as well as the health of the global ecosystem. These trace gases include toxic chemicals and greenhouse gases from both anthropogenic and natural sources. Accurate measurements of their emission flux are essential for better understanding the major sources/sinks or processes/mechanisms controlling emissions and further developing mitigation strategies. This chapter reviews chamber methods for the direct estimate of vapor flux from soil surfaces to the atmosphere in open fields. Two types of commonly deployed chambers, static (or closed, passive) and dynamic (or flow-through, active), are discussed according to their design, operation and major factors affecting flux estimate such as model selection, pressure deficit, flow rate, temperature and water condensation, etc. These “chamber effects” must be minimized to obtain the flux estimates best approximating ambient conditions.