practical laminar flow benches

[John Griessen]

On 07/16/2014 02:55 AM, Matt Harbowy wrote:> Why not figure out how to do it better and safer and cleaner? Wouldn't that be a much
better accomplishment?

Yes, that would be a great thing to discuss. Usually does not get much air time here though.

I have plans to make a shippable some-assembly-required laminar flow bench without a
ducted building exhaust as a product and include a particle counting method with it -- for cheap.
The particle counting is the essence of doing something research worthy with it, so you can qualify it for use
for a purpose and predict whether particles will land on your Petri dish for example.

So -- any suggestions on particle count estimators for qualifying HEPA filtration statistics?
I know the providers of filters say they test them by spraying the outside or intake side with glass sphere
dust, then count after collecting for a time at the output side. Anyone seen that done? Know what's needed?

Do they work like a spectrometer to figure out particle size as in the blueness of small smoke particles?
Are they based on digital camera CCD chips, or CMOS camera chips?

[Patrik D'haeseleer]

The mushroom and plant tissue culturing communities have lots of good DIY laminar flow hood designs. Here's two great guides:

http://www.fungifun.org/English/Flowhood

http://www.orchideenvermehrung.at/english/lfh/index.htm

As for 

[André Esteves]

Particle or Dust detector?

Maybe something like this?

www.seeedstudio.com/depot/Grove-Dust-Sensor-p-1050.html?cPath=25_127

André Esteves

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[John Griessen]

On 07/16/2014 11:29 AM, André Esteves wrote:
> Particle or Dust detector?
>
> Maybe something like this?
>
> www.seeedstudio.com/depot/Grove-Dust-Sensor-p-1050.html?cPath=25_127

> <http://www.seeedstudio.com/depot/Grove-Dust-Sensor-p-1050.html?cPath=25_127>

That says, "The output is for PM whose size is around 1 micro meter or larger. We can use the sensor to detect the dust in clean
room. "

so, it sounds very good. The outcome you want for ensuring your filter is really good is to
see few particles when flooding the filter intake side seams with a certain size of micrometer spheres
to see if any or 'how many' get through. $16 in small quantities is a good price.

Thanks for this lead to finding components.

[John Griessen]

On 07/17/2014 03:39 AM, Patrik D'haeseleer wrote:
> The mushroom and plant tissue culturing communities have lots of good DIY laminar flow hood designs. Here's two great guides:
>
> http://www.fungifun.org/English/Flowhood
> http://www.orchideenvermehrung.at/english/lfh/index.htm

I'll be sure to review those, thanks!

[CindyB]

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. 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 is the goal of laminar lab bench? "Nothing gets out?" " Nothing gets in?" Something else? That goal could be the best driver for identifying the best, low-budget effectiveness test.

Cindy

[John Griessen]

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

What is the goal of laminar lab bench? "Nothing gets out?" " Nothing gets in?"

Nothing gets in is the goal -- keeping your cultures sterile and clean
while allowing some particles or mist of them to flow out.

[Nathan McCorkle]

On Fri, Jul 18, 2014 at 11:00 AM, John Griessen <jo...@industromatic.com> wrote:
> What is the goal of laminar lab bench? "Nothing gets out?" " Nothing gets
> in?"
>
> Nothing gets in is the goal -- keeping your cultures sterile and clean
> while allowing some particles or mist of them to flow out.

Actually the goal of laminar flow is that nothing gets IN OR OUT. If
you're designing for nothing to get IN, it is much easier, which is
all Dakota cared about (he specifically mentioned this, but used the
word 'laminar' instead of just 'clean air', likely as that is possibly
where he sourced the unit from).

Laminar flow means a sheet of flowing air, the sheet carries anything
floating inside OR outside into a chamber and past a filter. It is
used for keeping your dirtiness out of your cultures, and keeping your
culture's dirtiness (i.e. infectious particles, to you or other
experiments) inside.

This level of bio has previously been discussed as not really
appropriate for home/DIY work. If you want to pursue this type of
work, you best learn a ton about PPE and BSL levels, infectious waste
handling, etc.

[Jason Bobe]

DIYbio.org's biosafety advisory weighed-in previously too:

http://ask.diybio.org/questions/is-it-a-good-idea-to-build-my-own-laminar-flow-hood/

One of their references included breakdown of laminar flow hood types, i.e. clean bench (protect specimens), biosafety cabinet class I or II (protect people!). 

Jason

[John Griessen]

On 07/18/2014 02:20 PM, Nathan McCorkle wrote:
> Actually the goal of laminar flow is that nothing gets IN OR OUT.
>

> Laminar flow means a sheet of flowing air, the sheet carries anything
> floating inside OR outside into a chamber and past a filter.

Umm... nothing gets *IN* is all I was discussing Nathan. No biosafety cabinet kits imagined.

The calm laminar, (in sheets), flow of air starts after the filter and any air diffusing
evening out slot patterns then flows through the chamber and out a door.
The door is outflowing enough clean air to continuously evenly push dirty
outside world air out the door so no dirt gets in that way.

There are types that intend to keep dangerous pathogens inside a box, but I am speaking of
the "keeps dirt out for culturing" purpose here.

[Nathan McCorkle]

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.