Pressure meters should be selected to read in what range

• A. -50 to +50 Pascals
• B. -100 to +100 Pascals
• C. 0 to 50 Pascals
• D. -25 to +25 Pascals

Answer: (A)

The key idea is to match the meter’s range to the expected pressure differences you’ll encounter, including both positive and negative values. In indoor environments, differential pressures between spaces are typically small and can swing around ambient, so you want a range that covers both directions with some headroom.

Choosing -50 to +50 Pa gives you symmetric coverage around ambient, so you can detect when one space is slightly pressurized and when another is slightly depressurized. It also provides enough room to handle typical HVAC operation, door openings, and external wind effects without saturating the instrument, while still offering decent resolution for small changes.

A zero-to-50 Pa range would miss negative conditions, which are common in building airflow scenarios. A narrower -25 to +25 Pa might miss larger but still normal differentials, while a much wider range like -100 to +100 Pa, though workable, would reduce resolution in the most commonly observed range and isn’t usually necessary for standard indoor testing.