Which measuring device is best for checking air flow rate from a grille?

The best device for checking air flow rate from a grille is the anemometer. An anemometer is specifically designed to measure the speed of air flow. It can provide readings in terms of volumetric flow rate, which is essential for evaluating the performance of HVAC systems and ensuring proper air distribution within a space.

Using an anemometer at a grille allows technicians to gauge the effectiveness of the system in delivering conditioned air. This measurement is crucial for maintaining comfort levels and energy efficiency. The other devices listed, such as a barometer, thermometer, and manometer, serve different functions—barometers measure atmospheric pressure, thermometers measure temperature, and manometers measure pressure differences—none of which can directly assess the air flow rate. Thus, an anemometer stands out as the most appropriate tool for this specific task.