# LEV calculations

## Conversions

 Enter a value and click on the button to convert to different units Inches = metres In w.g. = Pa kPa = In w.g. ft/min = m/s In w.g. = KPa Pa = mm w.g. cu.ft = m3 In w.g. = mm w.g. cfm = m3/s

 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 Molecular weight Working temperature °C Vapour Pressure Concentration Pa ppm mg/m3

## Averages

 This calculator will accept a series of numbers and display the total and average values. 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 To change this, just select an option from the drop-down menu. 0.01 0.10 As is Values Number of entries: Total value: Average value: Acceptable range at ± 20 % of average value Min: - Max: - Actual 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 air velocity of m/s, through a circular duct with a Circumference Diameter Radius of m Radius Diameter Circumference Area Volume Flow m m m m2 m3/sec

 ...through a rectangular duct m by m Note: A booth or fume cupboard face may be likened to a rectangular duct. Area Volume Flow m2 m3/sec

## 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 m m m m3/sec Air Change 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 °C mb Air Density = 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 Pa Pa kg/m3 Velocity = m/s