Impulse jet fans - pros and cons

[shaunmckeever]

I am looking for a little bit of guidance on the use of impulse fans in basement car parks. I know very little about impulse fans and would like to know what the pros and cons are. Are there any standards available including NFPA?

Thanks

[wee brian]

I think they areworking up a standard.

Some of the claims are a bit suspect. It depends what you are using them for.

[shaunmckeever]

I am working on a project in the middle east where their use for smoke clearance in a basement car park has been proposed. However I am interested generally on the pros and cons of impulse jet fans both for smoke clearance and smoke control.

I have seen the videos produced by Colt on tests they did in Middlesborough and Bristol. The videos did not seem very convincing. I am also aware that the fans may actually increase the volume of smoke (albeit less dense smoke) by pumping fresh air into the smoke layer.

[wee brian]

They are no good for protecting means of escape. They have some benefits in that smoke can be driven to one end of the car park. This may be of benefit for fire fighting.

To be fair the conventional spec is pretty pants so it all depends on what you are after.

[ashleyLFC]

Hi, check out the new BS 7346 part 7 2006, into being last October.  I've had some experience in my enforcing area of vent fans in basement car parks, smoke clearance so far, but developer is increasing to smoke control sites.  One main point is to check the CFD analysis.  Happy to discuss.

[shaunmckeever]

Thanks Ashley, I have looked at it. It is useful. I do have questions about how impulse fans might affect a number of things which the standard does not really address e.g. such as the the heat source from a car fire, can it be moved by the fan thus causing additional sprinklers to operate; what happens to the incoming air from the ramps where the cars enter the car park; is there any independent experimental data available to demonstrate their effectiveness in smoke clearance; can the pressure behind the fans force combustion products into stairwells; in multi-level basement car parks will the fans force air up (or down) into other levels; if you just had an extract system will smoke move towards the extract duct without the assitance of the fans anyway. Lots of questions. I just trying to pre-empt questions that might be asked by the local fire authority.

[Tom Sutton]

There is an article in The Means of Escape Journal on this subject may be of interest.

http://www.means-of-escape.com/articles/article147.aspx