The FlowBox is a passive exhaust fan flow meter that utilizes the DM32 manometer to measure exhaust only flows. This tool is perfect for measuring flows for bath fans, kitchen exhausts, room returns and whole-house ventilation. Its increased coverage area makes it easier to measure larger bath fan models with light assemblies. With all the holes plugged, the FlowBox can also be used as a pressure pan to locate leaks with a blower door. This is the only exhaust fan flow meter that can be used as a pressure pan without the need for tape.