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LEV calculations

Useful calculator for LEV assessors


Inches =
In w.g. = kPa = ft/min =
In w.g. = Pa = cu.ft =
In w.g. = cfm =

Convert between Pa, ppm and mg/m3
Enter the molecular weight and the working temperature, and one only of vapour pressure (Pa) or airborne concentration in ppm or mg/m3

Pa ppm


Enter a value, click on the button or hit [Enter] and repeat.

This calculator is optimised for face velocity readings in m/s to 2 decimal places so there is no need to enter a decimal point.

eg A value of 145 will be transposed to 1.45; 26 will become 0.26 etc

Min: - Max: -
range of values
Min: - Max: -
Warnings: None

Volume flow

This calculator will determine the volume flow through a duct.

Note: The duct wall is considered to be of negligible thickness

The volume flow for an of m/s, through a of

Radius Diameter Circumference Area Volume Flow

...through a rectangular duct by

Note: A booth or fume cupboard face may be likened to a rectangular duct. Area Volume Flow

Air change rate

This calculator will determine the air change rate in a room.
Enter the room dimensions and extract rate and click on the button.

Height Width Length Extract Rate
= changes/hour

Air density

The standard air density at 20°C and 1013mb barometric pressure is 1.2 kg/m3.
Enter a different temperature or pressure value in the appropriate box.

Temperature Barometric Pressure
= kg/m3

Air velocity

Calculate air velocity, metres/second from pressure difference (Pitot)
The standard air density at 20°C and 1013mb barometric pressure is 1.2 kg/m3.

Enter pressures and any different density value in the appropriate boxes.

Total Pressure Static Pressure Air Density
= m/s
Updated 2021-03-10