It all started when the people I live with started screaming at for fumigating the entire bathroom with lysol and telling them they can't take a shit right now.......

One will get sick and tired of cleaning fast when you need to sanitize an entire room to innoculate something quick and simple like a karo jar.....
It just got pointless to keep converting my bathroom to a cleanroom and back again everyday......I'm dying of the bleach fumes here!!!!

so I start thinkin.......flowhood. Yeah thats the answer, I say! So I asked Hippie3 about it and he said his ran him about 500 dollars...............

"Screw that!", I'm thinking, so I decide I can do it for cheaper. So thats what this photo essay is about, building an affordable flowhood.........and not making all the mistakes I did. So now we walk thru Dirtywop's path to enlightenment.........

Now....for starters, the concept of a flowhood is to eliminate contams by blowing a filtered, sterile breeze of air across an area, thus achieving positive pressure across that area, forcing all tainted air out and not allowing it back in, and allowing for sterile procedure to take place in that breeze. This is accomplished by blowing a strong air current thru a 99.99 effient HEPA filter and across the area in which you will do your work.........

But in order to achieve optimum laminar flow (a sterile breeze at a high enough velocity to make positive pressure-ie. 100 ft/min) , one must match the correct blower to your HEPA. And this is where I started. I first did some reading here.
For further reading on matching blowers to filters read pgs. 347-352 of TMC. That helped me a lot. So after a little bit of math that I won't go into here, I went ahead and bought a 275 cfm squirrel cage blower on ebay with a mountable metal housing for 25 dollars. Mark that as the first expense on our list.....

Now, the filter. This was a pain in the ass. I must have went thru 20 different monster corporations trying to get one filter shipped to me within the week. It was always either 4 weeks for delivery, or sold out, or this problem, that problem, have to be a business entity, have to order quantity, etc., etc.......So I quit playing email/telephone games with the these shmucks and decided to go with quality. So I went to Fungi Perfecti and ordered a 12 X 12 x 6 inch filter for 100 bucks even including shipping. Jim from FP is a nice guy. Those filters are 99.99% efficient too, much better than all the industries I dealt with. No need to cut corners on the most important part of the op, you dig? So now I've spent 125 bucks.


This is the part where I needed to come up with a design that would accomodate my odd blower box. After reading Nan's post in the archives, I decided to build this thing from plywood like I ought to. I referenced this animation......








But I changed it. Turned it around. The draw on my blower box is on the back, rather than the top. Otherwise than that, the only difference between mine and this one is shape and orientation. Here is a drawing that I started with.......



So it's off to the lumber company. I don't know much about wood so I sort of looked like a fool when he asked me what kind, and what for? Anyway I bought a sheet of plywood and a two by four. That came to less than twenty bucks. As it turns out, that one sheet was exactly enough to construct this thing. So our tally is now around 145 bucks.

My next step was to borrow tools. I got a t-square, a tape measure, a better jigsaw and skillsaw from a friend. I was straight on the screw gun. O yea, little stuff.....screws- 5 bucks, caulk-2 dollars, wood glue-3 dollars, 4 bolts- 2 dollars......there you have it. Excluding paint, we have all the materials needed to build a laminar flow hood and only spent 158 bucks! How about that! Ain't that sumthin!

You should have seen this DirtyWOP trying to be a carpender! Ha, what a laugh:lol: But I got it done eventually.....only minor mistakes in places it doesn't really matter! HOORAY!

here is an open pic of the front showing where the air goes when it leaves the blower

here is the back of the blower box, minus the fiberglass pre-filter, exposing the blower motor which powers two squirrel cage fans.......


and finally, an overhead view of the ~almost~ finished product
All the cracks were caulked generously and screws were screwed where screws were needed. All in all it turned out rather well. I thank everyone who helped me. Smooth Sailing from here on out. I will post pictures of my impeccable cultures for you to drool at.

can't beat it for 158 dollars!!!

No Wait....I forgot one thing........add on a few bucks to that talley

A tap light was attached to the top of the workspace for light. Takes two AAs and supplies ample light at a simple tap. Now all I need is a clapper smile.gif


How exactly are you going to use it? Does it set on a table what?

Is a flow hood of this type better than a glovebox? It looks great but what is the preformance like?

Good job Wop! I might just have to build one myself smile.gif
Keep it up... biggrin.gif


yup. It sits on a table, I sit in front of the table in a chair.
It is a lot like a positive pressure glovebox....
But I'd say it's better than a glovebox because of the open workspace. If there is one thing I hate it is a glovebox. They are just akward. It is very hard to get your hands in the side, be able to see well thru the top at the same time, and still keep yourself steady enough to plan your movements....I end up sweating and shaking and shit

with this guy, it's a breeze! You can sit back in your lazy boy and work right in front of it. And flow hoods actually have laminar flow, gloveboxes can achieve partial positive pressure, but only so much as a tiny computer fan can push....I think the lysol is what really does the job in the 9er glovebox....

with a flowhood, there is no lysol, and there is a 99.99% chance that NO contaminant mold or bacteria can make it thru that filter. That is why I built it. It's just an easy ride.

I haven't tested it yet for performance, for I have yet to even insert the filter. Until I do that, I can't even be certain that I didn't fuck up my math or if it will push. But it should be right. I was meticulous about making that filter housing exactly the right size. The filter ought to slide right in and be air tight.

I get the filter tommorow. Then I will leave a sterile grain jar and pitri dish open in the hood to see if any contams appear. If they don't, I know it works...............stay tuned...........
btw. nan - great contest thanks

I'm stuck on one thing tho...
when I insert the filter, I have no way to get it out. That is bad, these filters require replacement every couple years or so. The back is screwed down, and the filter just slides in snug thru the front.......I need some way to pull it out.
any ideas?


You are dead on with your explanation of the comforts of a good flow hood. My gripes and complaints about gloveboxes mirror yours exactly too.

On the filter release... Unless you can figure some way to slide it out, I guess you have to take it apart. Sometimes you can put a screw in the side of a filter and attach a wire to draw it back out of a slot. But I am not sure exactly on how you have it mounted.

First class project. Very nice presentation. wub.gif wub.gif wub.gif

P.S. Give us more? devil.gif


very very nice.

one minor change i would make,

i would have cut a slot to slide the filter in through the top or side.

i would use half inch strips of wood along the inside all the way around, on both in and out sides of the filter, to provide a snug fit, and hold the filter in place.

insert the filter, cover 'slot' with duct tape if it leaks.

in order to remove filter, remove duct tape and slide it out.

i would also paint the interior and exterior of the box.

if you look at air conditioning and heating ducts with filters in them, you might notice slide in filters, and maybe even older electrical ionizer type slide ins.


Yea....coulda shoulda woulda
but there is no duct tape allowed in this project wink.gif

I'll be painting it shortly
what sort of paint is waterproof?
O by the way I should add 5 bucks to the total tally for the pre-filter....
I forgot

Malformed: I think oil based would work best if its going to have more than just casual contact with liquid.
otherwise i would just go with a basic latex based paint (latex is cheaper anyway)

Pixie: big fan of kilz base coat otherwise you may paint that thing fourty times before you get coverage

Nanook: Use polyurethane... 2-3 good coats will seal the surface smooth as glass and it holds up to strong sanitizers, alcohol, etc.


thank you everyone
I think I'll do the inside with urethane and the outside w/ kilz.......

houstin...............we got flow biggrin.gif