Tunnel Ventilation — Portal Recirculation Check
Construction ventilation check for a portal recirculation check: velocity, air age and duct delivery.
Exhaust ducts that discharge too close to the intake portal feed the tunnel its own fumes — the construction-site version of a snake eating its tail. The separation rule of thumb (≥20 m and downwind) is geometry, but this dilution check quantifies the penalty when the site layout can't comply.
Formula
Note: Mine ventilation is statutory and life-safety territory: airflow quantities, gas limits and re-entry times must be set by the registered ventilation engineer/manager under your jurisdiction's mining regulations — this calculator is a planning and training aid.
Construction ventilation check for a portal recirculation check: velocity, air age and duct delivery. A free mine ventilation & air quality tool — no sign-up, no upload, instant results in your browser.
About Tunnel Ventilation — Portal Recirculation Check
Tunnel Ventilation — Portal Recirculation Check computes the governing relationship v = Q/A · air age = V_tunnel/Q live as you type. Exhaust ducts that discharge too close to the intake portal feed the tunnel its own fumes — the construction-site version of a snake eating its tail. The separation rule of thumb (≥20 m and downwind) is geometry, but this dilution check quantifies the penalty when the site layout can't comply. Defaults are pre-filled with realistic values for this exact scenario, and the worked example substitutes your numbers step by step so the math is never a black box.
How to use Tunnel Ventilation — Portal Recirculation Check
- 1Enter your values — Drive length, Tunnel cross-section, Airflow delivered at face, Minimum velocity required (sensible defaults are pre-filled).
- 2Read the live results: Mean return velocity, Nominal air age.
- 3Check the "with your numbers" line to see v = Q/A · air age = V_tunnel/Q substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Tunnel Ventilation — Portal Recirculation Check?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula v = Q/A · air age = V_tunnel/Q with authoritative sources cited on the page (McPherson, M.J., Subsurface Ventilation and Environmental Engineering; BS 6164 — Health & safety in tunnelling)
- ✓Exhaust ducts that discharge too close to the intake portal feed the tunnel its own fumes — the construction-site version of a snake eating its tail.
- ✓SI ⇄ Imperial toggle converts your inputs in place, so you can work in the units your drawings use
Frequently asked questions
What formula does the tunnel ventilation — portal recirculation check use?+
It evaluates v = Q/A · air age = V_tunnel/Q, exactly as published. Sources: McPherson, M.J., Subsurface Ventilation and Environmental Engineering; BS 6164 — Health & safety in tunnelling. The substituted worked example on the page lets you verify every step against the textbook.
How should I read the result — and how far can I trust it?+
Exhaust ducts that discharge too close to the intake portal feed the tunnel its own fumes — the construction-site version of a snake eating its tail. Mine ventilation is statutory and life-safety territory: airflow quantities, gas limits and re-entry times must be set by the registered ventilation engineer/manager under your jurisdiction's mining regulations — this calculator is a planning and training aid.
When is this calculator the right tool for the job?+
Construction ventilation check for a portal recirculation check: velocity, air age and duct delivery. A free mine ventilation & air quality tool. The separation rule of thumb (≥20 m and downwind) is geometry, but this dilution check quantifies the penalty when the site layout can't comply. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Does it support both metric and imperial units?+
Yes — the SI ⇄ Imperial toggle converts the values already in the fields, preserving the physical quantity, so you can flip mid-calculation without re-entering anything.
Related tools
- Airway Resistance — Concrete-Lined Shaft
- Airway Resistance — Unlined Rock Drift
- Airway Resistance — Timbered Drift
- Airway Resistance — Conveyor Drift
- Airway Resistance — Ventilation Raise (Bored)
- Airway Resistance — Old Workings (Leakage Path)
- Airway Resistance — Decline Ramp (Trucking)
- Paving QC — Season Shutdown Temperature Ledger
- Fire & Finish — Steel Punch-List Effort
Related Manufacturing tools
Spindle Speed Calculator — Aluminum 6061
Carbide starting RPM for milling Aluminum 6061: n = 1000·Vc/(π·D) with a handbook cutting speed preset.
● LiveSpindle Speed Calculator — Mild Steel 1018
Carbide starting RPM for milling Mild Steel 1018: n = 1000·Vc/(π·D) with a handbook cutting speed preset.
● LiveSpindle Speed Calculator — Stainless 304
Carbide starting RPM for milling Stainless 304: n = 1000·Vc/(π·D) with a handbook cutting speed preset.
● Live