Room Pressure Cascade Calculator

Plan positive and negative rooms with confidence daily. Tune airflow offsets using simple leakage inputs. Generate clear tables, CSV, and printable reports in minutes.

Calculator
Use the grid fields below. On large screens you’ll see three columns, then two, then one.
This zone is treated as 0 Pa.
Step differentials and setpoints follow this unit.
Multiplies the offset airflow (e.g., 1.10).
Typical: 1.2 kg/m³ at standard conditions.
Common range: 0.6–0.7 for cracks/openings.
Keep cascades modest. If you need high dP, provide relief paths.
Rooms in cascade
Each row defines a step relative to the previous zone.
# Room name Sign Step dP ELA (cm²) Supply (L/s) Exhaust (L/s) Note Action
1
Relative to previous zone.
Equivalent leakage area.
2
Relative to previous zone.
Equivalent leakage area.
3
Relative to previous zone.
Equivalent leakage area.
Reset After calculation, exports appear in the results panel.

Formula used

The cascade is built by accumulating each step differential:
Pi = Pi-1 ± dPstep,i with the reference zone set to 0.
Offset airflow is estimated from leakage at the step differential using an orifice model:
Q = Cd · A · √( 2 · |dP| / ρ )
  • Q is leakage flow (m³/s), reported as L/s.
  • A is equivalent leakage area (m²). Input uses cm².
  • ρ is air density (kg/m³). Cd is discharge coefficient.
  • Required net offset approx sign · Q · safety factor.

How to use this calculator

  1. Set a reference zone (often a corridor) and choose your unit.
  2. Add rooms in the order air should cascade through openings.
  3. For each room, choose + or − and enter the step differential.
  4. Enter equivalent leakage area to estimate offset airflow.
  5. Optionally enter baseline supply and exhaust for adjustments.
  6. Press Calculate. Results appear above.
  7. Use exports to document the run.
Planning tool only. Field testing is required for commissioning.

Example data table

RoomSignStep dPELA (cm²)Supply (L/s)Exhaust (L/s)Design note
Lobby+560140120Positive to corridor
Stair+2.5459080Smoke control buffer
Toilet-108060140Odor containment

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.