How much air is 400 CFM? That’s an interesting question.
To better understand the answer, first we’ll look at the concept of CFM and how it applies. It might be better to ask, how many compressed air using devices can I run with 400 CFM?
For example, if a compressed air drill uses 20 CFM of compressed air to run, then, in theory, you could run 20 drills at the same time with an air compressor that generates 400 CFM.
Or, a big sand blast cabinet might use 200 CFM of air when parts are being sand blasted. If you have two of these sand blasters running at the same time, then you would use up all the air a 100 HP air compressor would deliver which is about 400 CFM.
For future guidance, typically, you will generate about 4 CFM of compressed air at 90 PSI per HP of electric compressor motor.
How much air is 400 CFM?
Is 400 CFM of compressed air at 90 PSI the same as 4 CFM of air at 40 PSI?
That has to be answered as yes and no.
When using compressed air at 90 PSI, and the air tool uses 400 CFM to run, then you will need 400 CFM at 90 PSI to run it.
If an air tool needs 400 CFM of compressed air at 40 PSI, you still have to deliver the flow and the pressure you need, yet if you have a compressor capable of delivering 400 CFM at 90 PSI, and the compressor tank is full of air at 90 PSI, then that air will last longer when using it at the 40 PSI level.
It is not enough to ask how much air 400 CFM is, without knowing at what pressure that 400 CFM is being delivered at. If delivering compressed air at 400 CFM and at 10 PSI, you would not be able to properly run an air tool that needed 400 CFM of air at 90 PSI.
In order to ensure that your air compressor can deliver the compressed air you need, you will need to know the flow of air required in CFM and the pressure that flow has to be at for a specific air tool or air tools.