1. Thrust Formula
Theoretical Thrust: T = ρ × Q × v_out
Where: ρ=1.2 kg/m³ (standard air), Q=volume flow (m³/s), v_out=outlet velocity (m/s)
Equivalent: T = ρ × Q² / A_out
Where: A_out = π × (D/2)² outlet area (m²)
Effective Thrust: T_eff = T × η_install
Where: η_install = installation efficiency factor k (0.70–1.00); free jet (ISO 13350 test basis) = 1.00
2. Longitudinal Ventilation Calculation
Tunnel Resistance: Δp = (λ × L/D_h + ξ) × ρ × v²_tunnel / 2
Required Total Thrust: ΣT = Δp × A_tunnel
Number of Fans: n = ΣT / T_eff
3. International Standards
ISO 13350:2015 — Jet fan performance testing: thrust T_m, input power, sound level, vibration ★ basis for thrust & efficiency
ISO 13348:2025 — Tolerances, conversion and presentation of technical data (grades AN1–AN4; tunnel/process typically AN3)
ISO 5801:2017 — Air performance testing, installation categories A–E (★ Category E is not applicable to jet fan product efficiency)
ISO 21927-3:2021 — Smoke and heat control systems, Part 3: powered smoke and heat exhaust ventilators (incl. impulse/jet fans; F200/F300/F400/F600/F842)
ISO 13347-1…-4 — Determination of fan sound power levels (basis for Lw)
ISO 14694 / ISO 14695 — Fan balance quality and vibration levels (category BV) and vibration measurement
ISO 7235:2003 — Ducted silencer laboratory measurement (insertion loss, regenerated noise, total pressure loss)
IEC 60034-1 / IEC 60034-30-1 — Rotating electrical machines — ratings, performance and efficiency classes IE1–IE4
Non-ISO references: EN 12101-3:2015 (European equivalent of ISO 21927-3) | NFPA 502 (road tunnels) | AMCA 250 (laboratory method) | PIARC 2019 (ventilation demand and critical velocity)
4. Installation Factor Reference (PIARC)
| Position | η Factor | Note |
| Free Jet | 1.00 | ISO 13350 test basis |
| Ceiling mounted, ≥1D from top | 0.87~0.90 | PIARC Recommended |
| Side wall mounted, ≥1D from wall | 0.82~0.85 | PIARC Recommended |
| Ceiling mounted, 0.5D from top | 0.75~0.80 | Restricted |
| Side wall mounted, 0.5D from wall | 0.70~0.75 | Restricted |