What is the gauge zone value range (INWB)?

• A. 1.5-2.5 INWB (2.0 +/- 0.5)
• B. 0-1 INWB
• C. 2.0-3.0 INWB
• D. 1-2 INWB

Answer: (A)

Gauge zone values are given in inches of water (INWB), with a normal pressure centered around 2.0 inches and a tolerance of ±0.5 inch. That means the acceptable range is 1.5 to 2.5 INWB. This specific range ensures a small positive pressure is maintained to protect spaces and equipment, and it defines when actions or alarms should be triggered if the pressure drifts outside. The other options don’t match this standard: they either start too low, end too high, or don’t center on the 2.0 ±0.5 tolerance, so they aren’t the correct gauge zone for INWB.