Containment Air Balance
Required net negative CFM via Q = 2610 * A * sqrt(delta_P) and recommended NAM count.
Example
You enter
- Target pressure differential (in wc) 0.02
- Estimated leakage area (in^2) 8
You get
- Required net negative CFM 21
Details, formula, and sources
Orifice flow Q = 2610 × A × sqrt(ΔP) (cfm; A in ft², ΔP in inches WC). Leakage area is entered in in² and converted to ft² (/144). Recommended NAM count = required_negative_flow / per-NAM rated CFM.
Classical orifice-flow theory; constant 2610 from ASHRAE Fundamentals derivation. IICRC S520-2024 §12 for containment guidance.
Orifice-flow derivations free in published engineering texts.
Estimate. AHJ and licensed professional govern.
Field names used by the API: target_dp_in_wc, leakage_area_in2, required_cfm
- Orifice constant 2610 from ASHRAE Fundamentals (sharp-edge orifice, dry air, sea level)ASHRAE Fundamentals
- Default ΔP target 0.02 in WC (negative pressure inside containment)IICRC S520-2024 §12