Ventilation Dilution Calculator

Calculate required dilution ventilation airflow (CFM) to maintain a target airborne concentration from a known contaminant generation rate.

Generation rate (mL/min)

Molecular weight (g/mol)

Specific gravity

Target concentration (ppm)

Safety factor (K)

Room volume (ft³)

Tab to move between fields

Required airflow (CFM)

19,218

Required airflow (m³/hr)32,651

Air changes per hour115.3

99% purge time (min)2.4

Vapour generation (cfm)0.05

Generation (pints/min)0.01

How to Use This Calculator

How the result changes with Molecular weight (g/mol)

Generation rate (mL/min): Rate of liquid solvent evaporation in millilitres per minute.
Molecular weight (g/mol): Molecular weight of the solvent or contaminant (e.g. benzene = 78, toluene = 92).
Specific gravity: Specific gravity of the liquid relative to water.
Target concentration (ppm): Desired maximum airborne concentration in parts per million.
Safety factor (K): Mixing/safety factor (K). Use 3-4 for good mixing, 6-10 for poor mixing conditions.
Room volume (ft³): Total room volume in cubic feet for air change rate calculation.

Required airflow (CFM): Dilution ventilation air volume needed in cubic feet per minute.
Required airflow (m³/hr): Equivalent airflow in metric units.
Air changes per hour: How many times per hour the entire room volume is replaced.
99% purge time (min): Minutes to reduce concentration by 99% at the calculated flow rate.
Vapour generation (cfm): Vapour generation rate in cubic feet per minute.
Generation (pints/min): Liquid generation rate converted to pints per minute.

Identify Input Parameters
4 parameters
Generation rate (mL/min) = 5, Molecular weight (g/mol) = 78, Specific gravity = 0.88, Target concentration (ppm) = 10 = 6 input(s) provided
Calculate Required airflow
Required airflow = (generationPintsMin * specificGravity * 403 * safetyFactor * 1e6) /
19218 = 19218
Calculate Required airflow
Required airflow = requiredCfm * 1.699
32651 = 32651
Calculate Air changes per hour
115.3 = 115.3