Duct System Parameters
Rule of thumb: Duct surface area ≈ 0.5 ft² per CFM for typical commercial systems. Enter actual value or use auto-estimate: —
Leakage Test Results
Leakage at Class
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CFM
Leakage Rate
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% of design CFM
Allowed Leakage
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CFM max
Test Result
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SMACNA Leakage Class Reference
| Class | CFM/100 sf at 1.0 in wg | Typical Application | Sealing Required |
|---|---|---|---|
| 3 | 3 | Pharmaceutical, clean rooms, high-pressure systems | All joints and seams sealed with mastic |
| 6 | 6 | Low-pressure commercial, hospitals, labs | All transverse joints sealed |
| 12 | 12 | Standard commercial HVAC (ASHRAE 90.1 default) | Major joints sealed |
| 24 | 24 | Residential, low-pressure systems | Tape only (not recommended for commercial) |
SMACNA leakage: Q = CL × (SA/100) × P^0.65, where CL = class value, SA = duct surface area (ft²), P = test pressure (in wg). ASHRAE 90.1-2019 Section 6.4.4.2 requires ≤ 4% total system leakage for systems > 400 CFM.