Which of the following direct pressure measuring instruments is most appropriately used for measuring pressures very close to atmospheric pressure such as boiler furnace draft pressure?

Correct Answer: Option A — Diaphragm type pressure gauge

Diaphragm-type gauges are highly sensitive to low-pressure differentials, making them ideal for measuring boiler furnace draft. Unlike Bourdon tubes, which require higher pressures to overcome mechanical stiffness, the large surface area of a diaphragm allows for accurate measurement of the very slight pressures found in combustion air systems.