FlyTrapCare Forums

Hey everyone,

So I decided to build my own flowhood after seeing several builds. I completed the first step today by acquiring the HEPA filter. I will update this thread as I progress so you all can see exactly how I build the flowhood and why I decide to do things the way I do. Hopefully someone else can benefit from this build, and hopefully others can offer my advice as I build it!

So, step one was acquiring the HEPA. I managed to find locally a 24" x 12" x 6" - 99.99% Efficiency @ 0.3 micron, and aluminum housing with rubber gasket.

Pictured here:


Next, of course is to find the right blower to match to the filter.

Then, the build of the frame. I've got access to a large supply of wood of all sorts of sizes. So hopefully I'll be able to find some good pieces.



Wish me luck!

Looks like a good start renesis! Good luck to you and let us know how it goes!

Hi renesis,

the trickiest part of building an efficient LFH is to find a blower that matches the HEPA filter, because you want the air to come through the HEPA filter at the right speed, not too slow, not too fast.
I have found a PDF with some exemplary calculations.

Hope this helps!

Hey NZL,

I did see that pdf from one of the other threads, it is extremely helpful and helped me understand what I need to do better. I believe I calculated it out that I need to supply ~200CFM @ 0.5 c.w. of static pressure.

Do I have to go with a squirrel cage blower style? Or can an in-line style of fan be used. I think I've found a 10" Utility fan that fits the bill, just not sure if its the right thing to use.

Hi renesis,

Sure you can use an inline fan, if you install it in the correct orientation to minimize turbulence.

The most important thing is, as the name says it, you get a laminar airflow. When your LFH is finished, it should blow as hard in the corners of the HEPA filter as in the center. When you've reached this effect, and the airspeed is about 50cm/s, you have an efficient flowhood.

Excellent, thanks for the diagram NZL.

Should I install some sort of a baffle to even out the flow of air (or at least to make sure the flow isn't stronger at the center of the HEPA filter)? Or would this just end up causing more undesirable turbulence?

edit: And this is the blower fan I was looking at:

10" Utility fan, needs to be hardwired in. I think its used for Barn ventilation mostly.

350cfm at 0
250cfm at 0.5 (a little on the stronger side)

If you build your LFH as in the top left of my diagram, a baffle is not necessary. The curve in airflow evens it out everywhere.
If you're gonna build it as in the lower half of the diagram, a baffle might be recommended.

Yeah, I think I will be going with the diagram in the top left. Mainly because it will take a lot less space building upwards than horizontally.

Thanks for the help! Seems like you've done your research quite well. I will try to pick up the fan pictured above tonight or tomorrow. Hopefully I'll get a chance to go find some good pieces of wood today as well - its supposed to rain for the next few days here.

Good luck!

Thanks!

I checked out the fan I posted above today. I didn't like it, the build quality seemed very cheap. So the hunt continues!

How much do you pay for the filter?

I got really lucky and found one in stock locally. It cost me $90+tax, the list price was $160, but it had been sitting at the place for years and they were just happy to get rid of it so they marked it down for me. They were also confused as to why I asked for such an odd size.

Also, I think I may have found a blower!

Wow! $90 is an awesome price! They don't have any more left that you could pick up for me and mail to me do they?

Matt wrote:Wow! $90 is an awesome price! They don't have any more left that you could pick up for me and mail to me do they?

Unfortunately not, they told me they only had this one - and it was a special order for someone else that didn't pick it up 3-4 years ago. They also told me their cost for this filter is $70, and that nobody manufactures HEPAs in Canada- since they're all imported from the states, they said 3-4 weeks is the standard order time. This was on par with every other company I checked with - $150-180 and 3-4 weeks delivery time. The company is TRI-DIM, I believe they have offices in USA as well - may be worth giving them a call.

Great, thanks for the information renesis!