[DIYbio] low cost positive pressure laminar flow HEPA filtered box

On 07/18/2014 04:30 PM, Nathan McCorkle wrote:> I think common lingo just calls what you're describing a clean air
> hood, nerdier folks call them positive-pressure hoods.
>
> I could be wrong, but that's been my understanding for the past 5 years or so.

A hood suggests a vent to a duct in the building, so I did not want to talk that way.
Leaving out the words laminar flow would be such low braggability...

So how's the new subject line sound?

On 07/17/2014 11:00 AM, CindyB wrote:
> If you flood your intake side with particles to see how many get through you will have used up the fouling capacity of your filter
> with your test.

There must be some way such tests are done without using up the filter, because some companies brag about it.
By flood, maybe I used the wrong, non-quantitative word. They probably do not use a shovel to add
test sphere particles, but a puffer, duster, air siphon mixer of some kind similar to a siphon spray gun for liquids..

In industrial manufacturing HEPA flow hoods, tests consist of:1) testing flow rate of air on the clean side;
> target: not too fast, not too slow 2) industry standard particle detector test on the clean side; target: no particles in
> detection range 3) pressure drop across the filter; target; not too high
>
> I didn't give quantitative targets because it depends on the industrial requirements. I could see a low budget way of assessing
> flow rate with a small strip of cloth as in a wind sock and a home made water manometer (for pressure drop). Not sure how to get
> the particle detection.

What do you think of this:
http://www.sca-shinyei.com/pdf/PPD42NS.pdf

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