GordoTEK
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Build it yourself laminar flow hood for less than $100! The mycology community will LOVE this!
🕑 Added 2023-02-10 19:36:28 +0000 UTC[Video is here] I just built something the mycology community is going to LOVE. But let me just start off with this... I think building this is pretty easy and I've already built more than a dozen of them. It takes a couple of hours and requires minimal tools, but if anyone reading this wants to make and sell them for other people feel free to drop a link to your listing in the comments.
For years it's always bothered me that laminar flow boxes were so expensive, out of reach for many young mycologists, but let's be real, they make everything so much easier and most serious mycologists have one. They can also be quite heavy (the one I've been using for years weighs nearly 90 lbs) and by no means portable, or even easy to move around your house. I came up with a design that is light weight, portable, has a powerful variable speed flowrate, and is PROVEN to work (unlike all the silly things out there like a furnace filter duct taped to a box fan haha, or a giant plastic bag taped to a small home air/hepa filter, nope that's not laminar flow, put your arms in there and your work is ruined). This design passes the flame test as shown in the picture above, even when it's not turned all the way up to max flow rate. It has a high quality fan and the HEPA filter is good for 2,000+ hours, which by my calculations means a lifetime of use if you were only using it for mycology work, but the filter can also be easily replaced if needed for as little as $18.
First, credit goes to an anonymous guy I'll call "Rob" who private messaged me about this on Instagram. He described the design he came up with that was the inspiration for my own design which I will share with you. Rob lives in Europe so I did my own research and found the parts that are easily obtainable in the U.S. This was easier said than done as I had to test numerous filters and fans before I found the legit ones. It turns out there are LOTS of fake hepa filters out there that don't actually work. I purchased an expensive Met One laser particle counter to test filters for this project, and PROVE that they were working as expected. As far as I know, I am the first person to describe such a low cost laminar flow hood and also provide analytical testing showing that it works.
Also I want to point out that I DID in fact film this project from start to finish, and I have now released a video version of this. In the video I show how to use the flow hood, particle counts in various positions, tuning the fan speed, flame test, etc. I also show video proof that the design works flawlessly (I have made numerous agar dishes with a 100% success rate and even exposed open agar dishes to the flow for 5 minutes before closing them and waiting to see what would grow on them (nothing did!). That combined with the Met One particle count results are pretty irrefutable proof. The Met One meter has a pump that pulls in air and it can measure the number of particles bigger than a specified size, as you can see in the picture above, the flow hood allows ZERO particles >1µm (one micron) in size through (for reference, trichoderma spores are typically 3 to 5 µm in diameter). As soon as I move the Met One device out of the flow, it jumps to showing thousands of particles in that air (I show this in the video).
(Note that using any of my amazon links helps support my work, which is much appreciated. By the way if you are ever going to make a big purchase on amazon you can come click any of my links first and it helps support my work even if the item you purchase has nothing to do with the link)
HOW TO BUILD IT: You only need 4 parts plus some tools!
Get a tote of your choice to match the filter(s) you will be using with enough depth to also house the fan you will be using. If you use all of the same parts I did, this is the best tote I could find: https://www.target.com/p/sterilite-66qt-clearview-latch-box-clear-with-purple-latches/-/A-13794509
Note that the tote has smooth/flat surfaces, many of the ones I looked at had grooves that would interfere. You can also find totes at Walmart and IKEA, it does not need to be clear.
Next you need a filter. This one is great but if its sold out there are more options below: https://amzn.to/3Gq94cK
Note all of the excellent reviews, this filter is very well built and even has a nice prefilter. It comes in a two pack, so you will either have an extra one in case you damage the first, or to use as a future replacement filter, OR you can actually use BOTH filters together on a larger tote and double the size of your flow hood. Also it comes with carbon filters, these could be used as prefilters (they also remove odors from your air) or you could take the carbon out and use it to make black agar. Regardless, this is probably the lowest priced HEPA filter on Amazon that is actually proven to work, as I said, there are many fakes so beware if you are tempted to order something different. For European or Australian readers, you might want to try this genuine Phillips filter (or try searching for "Fy1410 Hepa Filter" locally) it's a little more expensive but nice size and I'm told it works (but the knock offs of this filter on Amazon DO NOT WORK), it's also on eBay shipping from Australia. And here is another filter in the UK that has been reported to work, and here is one reported to work by an Australian patron (sold by IKEA so possibly available in other countries too).
***UPDATE: if the HEPA filter I linked to above is sold out the following look identical and have great reviews, and some are sold as single pack instead of 2-pack so it's cheaper for the person that only wants one filter: https://amzn.to/3zOPjYg(single) https://amzn.to/409qOQF (single) https://amzn.to/3Z3rMNU (double) https://amzn.to/43kTatW (double) https://amzn.to/3Ibp837 (double). I have now tested these and they work just as perfectly as the original in the video!).
You will need a good fan, preferably plug in ready and it should have variable speed. This is a great deal, again note the excellent reviews: https://amzn.to/3RPtMXO it also has a nice speed control dial and it's rated to move 428 CFM (that much power is not needed initially but could be useful over time as the filter ages and more pressure is required to produce the same air flow).
Note: if this fan is sold out (click "see all buying options" first, there may be some from amazon warehouse) this one has similar specs and variable speed (important) but reviews aren't as good and you might have to drill holes in the housing to bolt it to the tote. One patron successfully used this fan for only $18 but it has far lower specs for airflow so I'm not sure its a great idea. In the UK/Europe I'm told this one is a good substitute but sadly you have to separately buy a speed controller for it so less than ideal).
To complete the job, you will also need some bolts and washers (can get from your local hardware store or Home Depot/Lowes) and silicone sealant ($5.99 is actually a great deal on amazon) as well as some course sand paper. The tools you will need (if you don't have something I would suggest borrowing from a friend who does): A caulking gun, a drill, any cutting tool (such as a rotary tool or jig saw or woodburning cutter or soldering iron), a dry erase marker and a screwdriver.
Temporarily place the filter (still sealed in plastic) inside the tote in the position where you want it to go, then use a dry erase marker to trace out the outline of your filter on the side of the tote, you only want to trace out the actual filter part, not the frame:
Use whatever cutting tool you have to cut along the lines you just drew. A rotary cutter seems to work fine and is less likely to crack the tote. I've also used a jig saw successfully but you need to drill a hole to get started. I show both methods in the video. Someone has also reported to me what using angled tin snips worked fine for all of the cuts in this project (even the round one).
Put the fan unit in the back bottom of the tote where you want it, with one end pushed up against the side of the tote (circle can be seen in above picture). Use the dry erase marker to trace out the circle of the fan then cut the circle out. This is nearly impossible with a jig saw as it will cause the tote to crack, but can be done with a rotary cutter if you are very careful, the circle does not need to be perfect. I've been told the plastic cutting can also be done with a woodburning tool using the 45 degree "leaf" attachment. That said, I also HIGHLY recommend using this hole saw with a drill:
TIP: Mark the center of the circle first and drill a hole there with a normal drill bit, then attach your hole saw, using the predrilled hole, RUN IT IN REVERSE this will grind out the hole with no cracking of the tote, works beautifully (I learned the hard way, destroying 3 totes before I got it right). I'll show how to do it in the video if this isn't clear.
Flip your tote upside down and notice the 4 bolts on the fan housing, put the fan into the hole you made in the tote with most of the fan inside the tote and just a small portion (1 to 2cm or a half inch) of the fan sticking out the side of the tote (see below picture), with two of the bolts on the fan housing unit facing straight up, mark the location of these bolts with a marker on the tote. Take the fan out, then drill holes only slightly larger than the diameter of your bolts where you marked.
Use sand paper and/or a file to smooth all edges where you made cuts in the tote, you can use your fingers to break off any blobs of melted plastic that formed from the cutting. Use sand paper to roughen the plastic around the holes that you cut.
Then clean the tote thoroughly with wet wipes or wet paper towels.
Put the fan unit back inside the upside down tote, with only a small bit sticking out the side. Use the new bolts and washers to bolt the fan to the tote:
Turn the tote back over (so fan is on the bottom) use the caulk gun and silicone sealant to put a bead of silicone all around the outside of the fan housing where it passes through the tote, get it from both sides of the tote (inside and out):
Next roughen up the front, top, and bottom of the filter frame with sand paper, being very careful not to touch the actual filter, wipe clean, then put a bead of silicone all around your filter frame and on the bottom of the filter. Stick the filter inside of the tote with the front pressed into the area you cut out. You can gently use both hands to push the tote from the front and filter frame from the back to seal them together, moving all around the filter frame. Add even more silicone sealant to the top of the filter where it meets the tote and down the sides of the filter frame inside the tote and the back bottom edge where it touches the tote. I now also recommend (not shown in video) adding a layer of good strong clear packing tape or duct tape or gorilla tape all around the filter top sides and back bottom, this helps secure it all in place preventing the silicone from coming loose if the unit is every banged around.
Cut a small notch in the back top of the tote for the fan cord to come out:
Then put silicone sealant all around the top lip of the tote and heavy where the slit is for the fan cord, then put the tote lid on and latch the handles down. Let it all dry for 24 hours, if possible let it dry in a garage or shed or outside as the drying silicone is kind of stinky.
That's it, you are done! I still recommend using good clean procedure when using your new flow hood. In the very least, turn off your home heating/cooling system to prevent forced air from blowing into the room while you work, wash your arms and hands thoroughly with soap and water, wear an N95/KN95 face mask, do not talk, sing, cough, sneeze, or rap while you work, wear new nitrile/vinyl/latex gloves sprayed down with isopropyl alcohol, try to work more toward the center of the flow, that usually means using an elevated surface such as a wire cooling rack or paper holder as shown above. Remember the air at the edges of the filter is turbulent and not completely filtered. Keep your work as close to the filter as possible without EVER touching the filter itself. Don't ever put your fingers/hands in-between the filter and your work piece. Only keep agar dishes open as long as absolutely necessary (that said I kept some open for 5 whole minutes in front of the filter just as a test and got zero contamination).
Note: It seems the air becomes turbulent at about 7.5 inches away from the filter with this design. No particles getting through at 7 inches from the filter, so that is your working distance with this unit. I have done agar plates, agar to grain jar, and grain jar to substrate inoculations all in front of this flow hood with 100% success rate so I know the working distance is perfect for mycology work. Also, turning the flow all the way up to max actually causes turbulent air too (particle meter clearly shows this) which indicates how important it is to have a variable speed fan. At max output, you will not have laminar flow at any distance from the filter really. Thankfully, you don't need an expensive particle counter to figure this out, you can do it all with a lighter! I will show this in the video. Using a lighter you can check that the flame bends at about 45 degrees or so, and remains very "steady" that is a great indicator of laminar flow, you will see the flame shaking in all turbulent zones, like at the edges of the filter or past 7.5 inches back from the filter. Where the flame shakes, you can expect high particle counts, where it is steady, zero particle counts.
Also note that "more flow" is NOT better, you want a very gentle flow, if you hold your hand up near the filter you should barely feel the breeze. You can fine tune the flow rate very easily with a lighter (preferably a long stem lighter), keep the flame in the general area you would do work from, you are looking for the exact point where the flame bends 45 degrees from the airflow and remains perfectly steady (no flickering or dancing). If you used all of the same components I did, this will be at the fan setting directly in the middle between "M" and "H".
I recommend keeping the flow hood covered when not in use, this is actually shown in the video (not yet published). The cool thing about the tote design is that the top edge/lip extends OUT a little bit so anything you hang over the top is not likely to touch the actual filter. You can use almost anything for this, a $1 plastic drop cloth (for painting) from Dollar Tree for example, or a towel or bed sheet, etc. This will prevent dust blowing around your room from landing on the filter. Always turn the flow hood on before removing the cover, and replace the cover while the flow hood is still on (turn off after cover is in place). It's also a good idea to work in the smallest room you can find to work in, and let the flow hood run for at least 15 minutes in that room before you begin working, this will clear the air of all small particles in advance.
If any of the above is unclear, it will become clear when you see the video. But I am happy to answer any questions and I will update this post for a while until it contains every detail needed.
UPDATE: You guys have already started sending me pictures of your homemade flow hoods and they look great. Here is an example with the Phillips filter that is more readily available in Europe and Australia:
(Love the artistic flair of the woman who made this one!)
(This person made the frame out of wood and made it a double filter design, he reports that the same ACInfinity fan I recommend is adequate to drive both filters. If you do it this way you will essentially have two separate laminar flow zones and you want to work toward the center of each filter, not in the center of the overall unit because there will be some turbulent air in the middle where the divide between filters is)
(This patron made a LOT of cool tweaks to the design, so many that I created a separate google doc for anyone interested: Jim the Corndodger Flow Box tweaks )
Notes related to the VIDEO version of this TEK: If anyone is looking for the Mycocoil (foot operated induction sterilizer) shown in the video it is here. And here's an example of the silicone tipped tongs that you can pressure cook and use for mixing grain spawn with substrate which is better than using your hands. If you want petri dishes that can be cleaned and reused, the glass ones are an option but often break in shipping, polypropylene ones are probably the better choice and they are less expensive.
Credit to: The Efficient Engineer (“Understanding Laminar and Turbulent Flow")
And more about Reynolds number
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Q&A Is it easy to change the filter? The manufacturer says it has a 4000 hour life, even if you cut that in half, it's probably still a lifetime of use for just mycology work for most people (remember you don't leave this thing on and running all the time). But yes if you had to replace it, it should be very easy to do so, the silicone sealant is like rubber cement, you can just pull the old filter off and scrape away the leftover sealant and put the new one in. Likewise the tote lid will still come off pretty easily if you pull on it hard enough. The whole replacement can be done in about 15 minutes.
Can or should I add a pre-filter? You could add a pre-filter if you want, you could do something simple like stretch a cotton t-shirt over the fan intake and secure with rubber bands or zip ties. Or you could use the carbon filter that comes with the HEPA filter. Its up to you. The HEPA filter is supposed to be good for 4000 hours, if only used for mycology work, that could be a lifetime for many people. But as noted above, the HEPA filter is not hard to replace if needed, it's basically a 10 minute job, can pull it off and scrape away any remaining silicone sealant, then put the new one on.
Can I use a bigger filter?
Yes, there are a couple of options for larger HEPA filters that may still work with the recommended fan, such as this one: https://amzn.to/4a0N7xl
There is also a much bigger one: https://amzn.to/3PP5JIX
but I'm not sure if the recommended fan will work with that one. But the truth is, you can do everything that is important with the recommended filter from the TEK, you can elevate the flow box for working with mycobags so the top of the bag is in the center of the laminar flow. Doing agar work, making grain spawn, and doing grain transfers is really all you need to do with laminar flow and you can easily do them all with a small laminar flow box.
I noticed some air coming OUT of the fan area, is that normal? First please make sure that you installed the fan in the correct direction because if you did it backwards the flow box won't work at all. But that said, yes, It's actually normal and expected for air to be flowing both in and out of the fan like that, this means the pressure has reached an equilibrium which is exactly what you are looking for, nice even pressure inside the box producing laminar flow out the front. You can very easily visually "see" the laminar flow by using a long stem lighter, you are looking for a nice smooth not flickering flame that is always pointed at a 45 degree angle no matter where you move it around the filtered air work area.
Can I install the fan in the back pointed directly at the filter? No, you don't want the fan pointing directly at the filter, this would cause uneven air pressure on the filter, you want it on the side and you will just allow it to build up equilibrium pressure inside the box (I probably should have explained that in the vid).
Is it an improvement to add a top and/or sides to the front part of the flow box? No, sides and tops are counterproductive, they create a vacuum and unfiltered air must then be sucked in to fill the vacuum, creating turbulence (the opposite of what you are looking for). You don't want sides or tops but its even worse if you direct the output into a still air box which for some reason many people seem to want to do (this completely defeats the purpose of a laminar flow box, you will have nothing but turbulent air).
Can I use the 6" or 4" version of that fan instead? The 6" model will work, the 4" will not. The HEPA filter requires around 200CFM but a little more is preferred, keep in mind that as the filter ages, it slowly clogs, requiring more and more CFM over time to produce the same flow rate.
I can't get that fan in my country or its too expensive here, is there an alternative? Yes, you can use almost ANY fan you are looking for minimum of about 250CFM. Some people have had success using cheap Dell computer fans but try to find one that has a listed CFM rate. Worst case you might have to get two of them. But you will need to add a variable speed control if it doesn't come with one for proper tuning. Its a bit more work but not too hard. You can use a "dimmer switch" to do the variable speed but you would have to do the wiring yourself. Many computer fans require a power supply sold separately.
Does the design really produce laminar flow? I've seen some critics saying the design doesn't produce laminar flow, but they are wrong. The design does in fact produce laminar flow when properly tuned, you can see this visually with a proper flame test (as shown in my vid at 18:53) and you can also see it with a smoke test, even though I didn't do an intentional smoke test in the vid, there IS actually an accidental one, if you blink you could miss it, but it happens at 25:48 as I'm sterilizing a scalpel that is smoking from the induction coil. As you will see, absolutely beautiful laminar flow! Compare this to other videos of smoke tests on laminar flow boxes. Most of the critics disappeared after hundreds (if not thousands) of people built these with absolutely fantastic results, there is no question that the design works well, many have called it a "game changer" for them. I think its funny that initially there were skeptics despite the fact that I show the design works by using an expensive laser particle counter, flame test, open agar plate test, and a complete start to finish grow with it. Producing laminar flow is not as hard as many once believed. But you do need a legit HEPA filter and capable variable speed fan.
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IN THE NEWS: Congrats to Australia! Based on the evidence, psilocybin and MDMA were just reclassified by Australia's regulators (like the FDA in the United States). Psilocybin can now for the first time be prescribed for treatment resistant depression and MDMA for PTSD. This is a major milestone. The US seems headed in the same direction. Hopefully enough doctors will understand this treatment option and have the proper training to guide their patients through it for maximal benefit.
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Links to all of my TEKs, Videos, Trip music, and frequently asked questions with answers can be found here: https://www.patreon.com/posts/22774475 (everything is made available for FREE, I do not use pay walls, support the work only if you feel like you've benefited from it and you are able to do so). People have told me my work has helped them overcome depression, addictions, PTSD, relationship issues, direction in life, and to have important, meaningful, sometimes life changing mystical experiences. I feel honored and blessed to play a small role in this. That is my reward.
Comments
GordoTEK
People have told me the laminar flow box was a "game changer" for them, you will love it, I've gotten overwhelmingly positive feedback, it really works and works well.
GordoTEK
Paper holders from office supply stores or amazon: https://amzn.to/3BhK6g9 (maybe find something similar at thrift stores or garage sales). Some cooling racks also work: https://amzn.to/3ZtekVk
GordoTEK
Sounds like you have a loose wire maybe? When you put the fan in the box maybe you are bending the power cord? You can probably fix it if you can solder, or return that fan for a new one. I have never heard of anyone else report this problem by the way.
Tiffany Logan
I just made one the same size with plywood and the fan refuses to blow in the box. Box is no bigger than this tote and works when outside the box. 😭
Gary
And where do you get these lovely little baskets that go in front of the filter?
Gary
I managed to get one quart jar of Pan Cyan to propagate using rye. Every other one just went nowhere or had contam. Hoping the laminar flow hood helps with this. It's going to change a number of aspects of the way I do things. Since so little grain spawn was produced, I will make a half batch using smaller totes. Still a few things to get from the hardware store and waiting on some deliveries from Amazon including the fan.
Gary
Okay, I'm going to give this a go. Converting one of my old monotubs into this. Just having the fan open with no filter is bugging me. Just going to suck everything into the back of my lovely laminar filter. Since I've got these nice carbon filters that came with it, I'll cut one down and put it across the air intake to block stuff from coming in. Yes this might inhibit airflow a bit but the fan has plenty of reserve suck power (like Linda but that's another story) so all should be okay, yes? I'd love to hear from anyone who tried this. Thank you.
Gary
I looked at your mods. You do good work. Thanks for sharing that.
Jca
No question the current tek is effective, as noted in the many examples that pop up on Reddit, YouTube, etc. I would build it out just for agar work it’s perfect. Small, portable, easy to manage. Raising it to work with 14T bags and quart jars is also workable. Where a bigger face would be most helpful is splitting 3# spawn bags into multiple 5# substrate blocks for gourmet cultivation. I looked at the 24X24 Vevor filter and if it were just the extra $100 it would make economic sense to upgrade. But the build out would need a custom cabinet 3 feet deep to house the filter and air box, and 3 feet tall to mount a much larger fan. The fan itself would need to push 400cfm against 1.2 inch static pressure. Thats in range of a 550cfm sealed squirrel cage fan and prefilter. Thats a lot of craftsmanship, time, and $400+, for a device that’s too big to move and will dominate any lab space we’re likely to have in our homes. I may still go down this route, but probably not until my process gets to the spawn bag and G2G level. That’s still a ways off on my journey, but it’s always nice to dream of what could be. Thanks Gordo for the great feedback and inspiration to learn new skills and experiment with the process. Cheers!
GordoTEK
Congrats, I know you will love it.
GordoTEK
Yes, there are a couple of options for larger HEPA filters that may still work with the recommended fan, such as this one: https://amzn.to/4a0N7xl There is also a much bigger one: https://amzn.to/3PP5JIX but I'm not sure if the recommended fan will work with that one. But the truth is, you can do everything that is important with the recommended filter from the TEK, you can elevate the flow box for working with mycobags so the top of the bag is in the center of the laminar flow. Doing agar work, making grain spawn, and doing grain transfers is really all you need to do with laminar flow and you can easily do them all with a small laminar flow box. I would not describe this design as "pseudo-laminar" but it doesn't have to be perfect. There is actually a point in the video where I inadvertently create a stream of smoke after induction heat sterilizing my scalpel and for a brief moment you can see the laminar flow kind of like a wind tunnel with a stream of smoke. The design does indeed provide legit laminar flow.
Curmudgeon76
Jca - I only just now saw this question. https://www.amazon.com/gp/product/B0B5B3B1DH/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 I see Gordo has added this item to the addendums to the flow hood TEK. If you pull up the TEK and scroll down to see what's been added, you can use his amazon link, thus possibly benefitting him (he's an Amazon associate).
Jca
What filter did you get? I’d like to take a look at it. Thanks 🙏
Curmudgeon76
I have found a 12"x24" H13 filter that is essentially a larger version of the filter Gordo used in his build. While the top to bottom laminar flow zone will be even smaller than Gordo's, the side to side will be much wider. I should be able to use the same fan. I'm debating using a carbon pre-filter at fan intake, or possibly an H13 pre-filter. I'm using the 106 qt Sterilite tub for this. Agar to grain in myco bags should work by laying the bag on it's side with the bag opening in the laminar flow. That is my hope.
Curmudgeon76
I agree that 18"x24" would be optimal for operating in a level of comfort, especially for agar to grain situations. I have had zero luck finding an H13 level filter in this size. The 18"x24" filters I am finding are thicker, around 2-2.5 inches, and will require a better fan.
Dan
Finished my Flow hood tonight. I got everything from Gordos links. I’m stoked!!!
Jca
Spent quite a few hours researching components, published literature, issues, concerns, problems, and conventional wisdom. Here is what I learned. This build produces a relatively small sterile field. Net of frame, the filter is roughly 12x10”. You’ll probably want to stay 2” away from the filter edges to avoid entrainment of contams from eddies forming on the flow boundary. All in, the sterile field likely starts 2” above the bench and is shaped like a squashed quarter-sphere 8” wide and 6” tall. This corresponds neatly with the Gordo’s particle count at 7” from the filter face dead center. Being an older noob, working under pressure, excitement, fear, there’s not much room for error. I’ve literally watched bench techs live, prepping assays in flow hoods, they never miss a beat. Pipette to plate, plate to stack, new plate, etc. Thats not me 😀 I need more room to fumble around. Probably I’d be OK spores to agar, and agar to agar. But put a quart grain jar or two in this small area and I’m done. Forget about a 13” tray for S2B. For those who have had success with this build beyond the agar stage, recall the bench techs above - deliberate, direct, not fast, not slow. My take away is that technique (mostly) trumps technology. For those of us learning technique, I feel like a larger build would be helpful, like 3x. I’m shooting for a net filter face of 18x24”. Besides finding a true HEPA with these dimensions (still looking), the fan spec is critical. Doing the math, I’ll need 300 cfm measured at the filter face to get 100 ft/min flow, the benchmark as I understand it. Static pressure of a HEPA and MERV 14 pre-filter is approx 1.2 inches H2O total. I have not been able to find a pressure curve for the Axial S8, but the mfg spec sheet states it is not appropriate for static pressure applications. They recommend moving to the significant more expensive closed blade model. Again, for those of you having success with the S8 on a side-by-side double filter build, I’ll say it again. Technique trumps technology. And then there is the old laminar vs turbulent flow topic. I know this is a long post, and I’m sorry to add to it, but I feel strongly that the conventional wisdom on laminar flow is misleading at best. Consider wind tunnel technology, where laminar flow is must-have, operating at extraordinary flow rates. These devices are linear, dimensions increase/decrease at specific points, have diffuser panels, and baffles. All designed to break up big, turbulent eddies into progressively smaller ones that dissipate before the laminar test chamber. That’s not what’s happening on the face of our HEPA filter. Instead turbulent eddies form at the pleats, where flow is substantially different between each convex pleat and its neighboring concave pleat. These eddies get bigger as they move away from the filter face, eventually turbulent flow becomes Reynolds dominant. Pleat eddies grow more quickly at the filter edges, where they interact with adjoining static air, and greater delta-v. This is where the larger eddies entrain contams, interact with smaller eddies further from the boundary, eventually entraining contams all the way into the center of the sterile field, albeit at some distance from the filter face (7”?). All of which is to say that our flow hoods are pseudo-laminar, which provides a shaped, sterile field sufficient to do our work. The design issue is not turbulence, it’s entrainment at distance from the filter face. So work close to the filter face, wear a mask 😷 and (I think) get a bigger filter.
Organizer
Hi Gordo, really great instructions. I've just finished my build (couldn't find your fan in Europe and mine is now complete overkill, but otherwise quite similar to yours). I rented a particle counter for a day to test it. The results are good. In the very center of the safe zone I even get 0.5μm counts to zero but I'm not always getting 0 at 1μm in some of the outer ranges of what I would like to call the safe zone (e.g. 5cm from the side edge). You stated the size ranges of a few things we want to avoid and they all started at 3μm so why would having 0 counts of 2μm particles not be good enough? Of course having 1μm at 0 would really give a high validity, I understand statistics, but couldn't we be happy with 0 cumulative counts per 60 seconds for 2μm particles?
GordoTEK
Yes it could be mounted on the top, just didn't seem very convenient to do it that way to me.
coloradoyeti
Hey Gordo. Are there any advantages to mounting the fan on the inside back corner vs outside on top? I have a backup variable speed 6" 408cfm inline fan that's a bit longer than the one in your video, so just curious. I like that compact design of having it on the inside!
Jim
Hi we have messaged a couple of times. Quick question. I have some cubensis trays just starting to pin and I need to go out of town for a couple of weeks. Could I just pop them in the fridge till I get home
Corndodger
While I'm up and writing, Gordo, are any of the great artworks you've shown available to us art appreciators?
Corndodger
I have the 2-pack Amazon filter set, which has a "black" filter and a Pleated Paper one you can see through. Question, which filter goes towards the outside of the hood - the pleated paper one you can see through, and looks like side facing out in the video, or the "black" filter? Or does it make a difference? Would appreciate a quick response, this is the last step to getting my hood up and running! - the Corndodger
Corndodger
I've just purchase the "2 filter" option from Amazon - it comes with 2 filters per filter, one a "black" one, the other with a pleated paper-like side, with a white fiber-like other side. You can see through the paper-like filter.
GordoTEK
I think I just found that at a thrift store, but you can find them at staples or on amazon, paper holder rack. Wire cooling racks might work too but you might have to put something under it to make it a little taller.
GordoTEK
Yea I believe it will work.
Steve Smith
Your techs have helped folks...Thanks
Jay
Thanks again Gordo. You make everything so simple. Just like life should be.
John Condron
I am thinking of using a larger tote and using two filters, one set horizontally, the other vertically, giving me two work areas, one slightly taller than the other. Do you think that would work?
John Condron
The originally recommended filters are available on Amazon right now, and they link to the second-choice fan (I just ordered both).
lagos tout
Hi, Gordo. What's the rack you use as a working surface in the video? Thanks!
Aditya pai
The fan seems a bit expensive here in the UK. Is just the inline fan that work or anything the produces about 200- 400 CFM? I've found multiple exhaust fans that give that kinda air flow and are much cheaper, they are just not the inline type.
GordoTEK
People who have tried this say the recommended fan is capable of driving both filters no problem.
ifeelcrumbs
I'm not sure where I saw it, but someone reported doing just that, and the fan used in the video was plenty with two filters, apparently.
JustiNourse
If I was to do two filters side by side, would I need a need a bigger fan?
David Earney
In the Amazon Frequently Bought Together recommendations, all of the items on your list are highlighted.
GordoTEK
Nice work!
GordoTEK
Nice to have another option.
JSquared
Building my own box as we speak! I'm being super cheap though and cutting everything with a $6 soldering iron from harbor freight 😜 (ventilation required!) I have a fume venting system for my soldering on other projects. So excited for everything to be done! EDIT: Built up the box and used it the very next morning. Inoculated two grain bags and scraped spores, from a print ;), onto agar. All three agar plates have mycelial growth with zero signs of contamination! For the price and ease of putting this together, it is so good! Thank you to "Rob" for the inspiration and Gordo for bringing it to our attention!
Dave Casey
This technique for cutting sterilite worked for the straight cuts. (I just used the drill for the round hole.) https://youtu.be/AbWUZYwYFN8
GordoTEK
Yes, the same fan can accommodate many different sizes of filters or 2 filters (I am guessing haven't actually tried the 2 filter configuration).
GordoTEK
Yes I did the flame test, will show extended version of flame test (even for tuning the fan speed) in the video. But no, I would not say the flame test alone is going to tell you if the filter is allowing particles through or not sadly, the only real way to know that is with a particle counter. If you can trust the manufacturer, or if someone else has done particle testing on the specific model, you are probably good to go. You could always try a random filter and just use it for agar work to see if it works or not too, but its a lot of work to go through for an uncertain result.
GordoTEK
Glad to see confirmation. Yea several people have already sent me pictures of their finished flow hoods.
GordoTEK
Yes absolutely, there will be a line down the middle between the filters though and you would probably want to avoid working in that area, basically you'd treat it like two separate work areas.
Humberto jimenez
Also do u use the same fam and just turn it up?
Humberto jimenez
Cool thanks for the confirmation? So did u do the flame test to test the laminar flow? I’m new to laminar flow but am I correct in assuming as long as the flame test is good then I have no reason to worry about contamination?
Scottman
I just did this and it worked 100 percent
Humberto jimenez
Could you find a bigger tub and put the two filters side by side for a bigger work area?
OldBrownWookiee
I’m gonna DM you Tep.
GordoTEK
Follow up: I measured this, and it seems the air becomes turbulent again at about 7.5 inches away from the filter. No particles getting through at 7 inches from the filter, so that is your working distance with this unit. I have done agar plates, agar to grain jar, and grain jar to substrate inoculations all in front of this flow hood with 100% success rate. Note: turning the flow all the way up to max actually causes turbulent air too, so this was a good experiment to do, and shows how important it is to have a variable speed fan. At max output, you will not have laminar flow at any distance from the filter really. Thankfully, you don't need an expensive particle counter to figure this out, you can do it all with a lighter and a flame test, you can actually observe when/where the laminar flow breaks down very clearly in the "shaking" of the flame.
GordoTEK
Yes that is also what I'm thinking, they are so remarkably similar it's very high likelihood they came from the same exact factory.
Jeesh
Appreciate it.
Jeesh
Thanks Gordo. I figure most should come from the same factory just wholesaled to different sellers, but I wasnt sure if you had any experience with any other filters
GordoTEK
I was afraid that might happen, looks like you guys bought out all of the inventory on the HEPA filter I linked BUT looking around I think the following all look identical and have great reviews, and one is sold as single pack instead of 2-pack so it's cheaper for the person that only wants one filter: https://amzn.to/3Z3rMNU (single) https://amzn.to/3IAhZcV (double) https://amzn.to/3xwv9kQ (double). Sadly I haven't tested these so can't guarantee it but just based on the pictures, reviews, and descriptions I bet they are identical and if I do more builds I will test these others.
Jeesh
Are there other HEPA filters that can work for this TEK? It appears the filters linked are sold out.
GordoTEK
Good questions, in the video I will show moving the particle counter all over the place, I will get back to you on the exact distance where the flow becomes turbulent and compare this distance at different fan speeds. I actually didn't do that in the original footage (but should have). At max the S8 fan is rated 428cfm, but I have no idea what cfm is actually coming out of the filter, it would be interesting to try to measure it but I'd have to research the best way to do that.
Tepezcohuite
Thanks for posting. The tek looks interesting. I have a few questions. 1. The particle meter looks very close to the filter. Do you have readings of particles at a working distance from the filter where one would be working with agar etc. 2. Would you mind showing the data vis-a-vis the CFM of the fan and the static pressure of the filter? Also can you show the CFM from working distance?
Michael
You’re the JAY Z of mycology. Man is innovative giving this culture what it needs. Thanks 🙏
Pierre Robert
This is great. Been scared to try agar until I saw this.
Old Bear
For anyone questioning the utility of a flow hood, I picked up a used EdgeGARD for $270 & it revolutionized my lab — I can cool freshly poured agar in Petri dishes to room temp with the lids off w/o contam. If my hood ever gives up the ghost, I’m making one of these.
Oakley
Hey this is awesome
GordoTEK
Yea, I HAD to know if these filters and fans were really adaquate and the Met One is really the only way to easily tell. It would take weeks to just do agar plate tests and even then it wouldn't be completely reliable.
Awaken Brain
Thank you for going to the trouble and expense of getting a Met One laser particle counter to test the filters. It satisfies my inner nerd. I appreciate the thought and effort you put into making a quality DIY that you are showing us works. looking forward to constructing my own.
GordoTEK
NO MERV rated filter is adequate for mycology use. Here is a good table that explains it: https://www.epa.gov/indoor-air-quality-iaq/what-merv-rating You need 100% capture of all particles over 1 micron in size. Now that said I know there are people using these MERV rated filters for mycology, they are definitely better than nothing and capturing 95% may work especially if you are working in a small clean room. But still I would not recommend it, get a true HEPA filter, the one I found is only $36 for a two pack so you really can't beat that.
Vecces
If Gordo was able to leave agar in forced air for 5 mins w no contam... then I'm going to give it a shot. Tired of anxiety inducing sab for old-man hands, eyes. A lot more relaxed. Hope people report on experience and successes.
GordoTEK
It's true that fruiting is not in a sterile environment but most mushrooms are like an inverted cup and the spores are slightly protected from falling dust in the air, if your growing environment had no obvious contamination and you harvest in front of a flow hood and put the caps on foil in front of a flow hood and then cover them, most of the time they are super clean and won't show contamination even on the very first plate. But yea if it dies, not a big deal to do an agar to agar transfer to clean it up.
Can Spengler
Gonna try putting one together and get it tested. I’ve got the parts coming. Might have to use a different fan and box. And will use a two filters.
Null Phase
not sure why people are so worried about keeping prints sterile. fruiting stage is not sterile so why would the spores that are produced be sterile as well? spores are inherently unclean and are cleaned by doing agar transfers.
Rumple
Thanks!
Dan G
Filterbuy.com has a wide range of filter sizes for relatively cheap, and free shipping over 100$. You can get a 12"x27"x4" MERV 13 filter for 45$, 12"x20"x4" filter for 35, with bulk discounts or thinner filters for less. I'm not sure how MERV 13 compares to the ones posted by Gordo. You could measure the whole face of one side of the tote, subtract a few inches, and get the whole side to be a filter. You could do this with different size totes too, the 105 qt tote (https://www.walmart.com/ip/Sterilite-105-Qt-Clear-Plastic-Latching-Box-Blue-Latches-with-Clear-Lid/46001911?athbdg=L1102) could accommodate a 27" wide filter (maybe a 30"), the 66 qt could probably do a 20" wide filter. Also, the size of the tote leaves a lot of unused volume, I'm wondering whether you would cut a square hole in the lid of a 32 qt tote (24"x16"x7" https://www.walmart.com/ip/Sterilite-32-Qt-Clear-Plastic-Latch-Box-Plastic-Stadium-Blue/585971677) and then use the tote propped up against a wall sideways and secured (the lid is not completely flat, so it may only be able to have a 16"x12" filter, can't be sure until you measure). The depth of the 32 qt tote would require a 6" fan instead of an 8" fan, but I'm not sure if thats enough CFM, judging from Gordo's post.
GordoTEK
I would use the filters unmodified and simply silicone seal them together but this does raise the question of what happens to the laminar flow along the center where they are joined? You might have to avoid working in the center which could be annoying. Further testing is required. But removing the frame could damage the filter and you will still have to join them together which implies a dead zone of airflow in the middle. Maybe not a great idea to use two filters like this but I think it could be nice as long as you work in the centers of each filter almost as if you just had two separate units sitting side by side. I think the fan used here is strong enough to support both filters.
Rumple
If using both filters to make a larger work area, would the frame on the sides where the filters meet need to be removed?
Wes D
Ahh I was just thinking positive pressure with clean air only coming in would be ok. Thanks!
GordoTEK
No, that is not a good idea, you want laminar flow and that would produce turbulent flow, as soon as you stick your arms in the box particles are flying everywhere, that leads to contamination. Laminar flow is the gold standard.
Wes D
True, anything would probably be better than nothing just whatever you can do to keep out excess dust. My other thought for when I make a new one is just to somehow do it a SAB style with the filter on the back of the SAB with the hand holes just like the SAB. Obviously it's no longer a SAB but it's just a thought I had. Kinda like an upgraded version of a SAB in my mind.
GordoTEK
I considered using the carbon filter as a prefilter but wasn't sure it would really contribute much, a furnace filter would make a better prefilter but I suppose the carbon filter might be better than nothing.
Nick Lang
Thanks 👍
kevin lee
Yep I noticed the same. AC infinity seems to be popular in the US. I wonder if there is a convenient UK equivalent. Also if you put this part number into Google you will find the Phillips filter:- Fy1410 Hepa Filter
Learn More
🎥🎬🤙
Nick Lang
Amazing. Will be trying this Checked the price of the fan in the UK, £98! ($120). Cheaper to get it shipped here from US
HD1237
On it!
Mike Padia
How much is it to replace the HEPA filter? Maybe it needs another, prefilter (bungee cord a couple pillow sacks with Poly-fil, keep it $100). You got to wrap carbon filters in plastic wrap or they stop working. Carbon filters are for smell (in a grow)? They also cost $50++ for 8" filter. Your $100 budget is blown.... Anyways, we can take "prints" and grain transfers (I've actually learned to do it over a warmed up oven 250°f for 15mins, the hot sterile air rises....) with this. The still air box is great for agar.......I ain't gonna change my hot oven tek for an air box 🤟
Mountain Myco
Outstanding! I love A/C Infinity fans.
Wes D
I'm not saying it's necessary but its worked very well for my setup
Wes D
Well this is stuff I already had. And in my mind would stop any dust or large particulates from entering your hepa, extending its life.
Mike Padia
OldBrownWookiee
Nice work!!
Shepdiggity
Thank you Gordo I have been wrestling with this mega purchase (flow hood) for some time and just couldn’t justify the expense for a hobby. I’m going to get right on this. Thanks again for all the support you give to the community
Wes D
Only thing I did different was attached a carbon filter to the intake like you would in your standard pot grow room. In my head I figured it was an extra layer of protection to make my hepa filter last longer. I've had great success 🙌
Wes D
This is exactly what I built last year lol hope I had a hand in the inspiration! Great job gordo!
Derek
Gordo you are seriously the GOAT MVP.
ben dulong
Cool!
