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Car Park Ventilation — Excel → Web Tool

Responsive single-file tool — mass-balance ventilation calculations, unit switching, validation, and export.

Inputs

Units Metric (m, m³/s) Imperial (ft, CFM)

Car Park Length

m

Enter length of bay/area

Car Park Width

m

Enter width of bay/area

Clear Height

m

Floor-to-ceiling height

Number of Vehicles Present

Typical occupancy at peak

Average Engine Running Fraction 5% (Mostly idle & engine off) 10% (Typical) 25% (High idling)

Fraction of vehicles with engine on (0-1)

CO Emission Rate per Running Vehicle

g/hr

Default 10 g/hr per running car (adjust as needed)

Target Indoor CO Concentration

ppm

Set allowable CO limit (ppm)

Outdoor CO Concentration

ppm

Background outdoor CO (ppm)

Air Changes per Hour (ACH) — (optional)

You may supply ACH to compute ventilation flow from ACH.

Design Safety Factor 1.0 (No factor) 1.2 (20% extra) 1.5 (50% extra)

Multiply ventilation by safety factor

Quick instructions:

• Fill length, width, height to compute volume (or override via ACH)
• Set number of vehicles and engine running fraction to estimate pollutant generation
• Press Calculate to compute required ventilation (m³/s or CFM)
• Switch units at any time — values auto-convert.

Results

Metric • m³/s

Floor Area

-

Volume

-

Estimated CO Generation (g/hr)

-

Required Ventilation (m³/s)

-

Required Ventilation (CFM)

-

Equivalent ACH

-

Recommended Supply / Exhaust Ratio

Supply ≈ Exhaust

Rounded Flow

-

2-decimal, thousand separators

Safety Factor

-

Applied to computed flow

Assumptions: Uses steady-state mass-balance: Q = G / ( (C_target - C_out) * 1.164 ) . - G = total CO mass generation (g/hr). The factor 1.164 converts ppm·(m³/s) ↔ g/hr for CO at standard conditions.

Made to be pasted into any site • Vanilla JS • No external libs