View Full Version : Supply and Extract Calculator

18-02-2013, 01:18 PM
Hi Guys and Gals

Just wondering if anyone has a easy way of working out what size extract or supply fan i would need for a certain area. i.e. if i take the room measurements how should i calculate it? it has always been something someone else has done. Any help will be appreciated


B G Scott
18-02-2013, 03:13 PM
Let us have the room details and also indicate the proposed use of the area as the ventilation rate is dictated by the application.

18-02-2013, 10:07 PM
You need to know the type of room occupancy from which you will be able to find the number of air changes per hour. A simple calculation from there on.

Or, with the power of our friend Google....


19-02-2013, 07:56 AM
The room is a Lab 3.5m x 5.3m x 3m high there is a fume extraction in place doing 4,000m3 per hour they need a simple supply to make up for the extraction

19-02-2013, 06:12 PM
I think that you have part of your answer within your own statement.

If the fume cupboard is running then they need something to replace the extracted air. If it's not running full time then perhaps some form of speed control is needed.

25-02-2013, 09:15 AM
Thanks for the help people

25-02-2013, 11:24 PM
A static duct from external of structure will assist fume cupboard extract. 4000 m3 / hr is 1100 plus litres per second. Which would create a semi negative pressure in area without static make up air, could have been an initial design requirement to reduce contamination in localized area.