Which device is used to measure air pressure in a compartment for ventilation control?

• A. Manometer
• B. Barometer
• C. Hygrometer
• D. Thermometer

Answer: (A)

Measuring air pressure in a compartment for ventilation control relies on a device that directly indicates pressure differences by balancing a column of liquid. The manometer does this: the pressure inside the space pushes on the liquid in a U-shaped tube, causing the liquid to rise or fall. The height difference corresponds to the pressure difference, letting you set or adjust ventilation to maintain proper flow and prevent unwanted pressure changes between spaces. A barometer measures atmospheric pressure outside or in the environment, not inside a specific compartment. A hygrometer measures humidity. A thermometer measures temperature. So for controlling ventilation by monitoring compartment air pressure, the manometer is the appropriate device.