How and Why a Laminar Flow Hood Works - Prevent Contamination for Cultivating Mushrooms at Home

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I've been dreaming of building a laminar flow hood. Not only do I love to build things, but I know that I could bring a lot more efficiency into my workflow for cultivating mushrooms at home, while also reducing the occurrence of contamination in my substrates. I dove a little deeper into the science of how and why a laminar flow hood is so efficient at preventing contamination, and wanted to share with you some of the things I've learned.
And yes, I now realize I spelled "efficiency" incorrectly...and "particulate". I'm trying to do science here, not write a book! lol

[@pu12eevil]

I know this is 2 years later. Reynolds number calculated for a pipe can be used to design this. It's Re = DVp/u where V is average velocity in the pipe, p is the fluid density u is the dynamic viscosity, and D is the diameter of the pipe. The trick is replacing the D with the equivalent diameter "De" which can be in this formula De = 1.3(a*b)^(.625)/(a+b)^(.25) where a and b is the cross sectional length and height of the box or in this case the filter. Real nice video man

[@EyeSea]

Very well explained, love seeing videos that educate in a timely and effective matter. Nice job!

[@wycliffbyonne6908]

Direct and to the point! I wish you would do video on measuring the "Re" flow. You got my subscription.

[@trof4904]

Simple, solid and good explanation, you earned my subscription!

[@tomasgemes4349]

Hoping you make a part two! Really really usefull!

[@kevinmunger1842]

I just became inspired to create a flow box. Going to use a 95 liter/80 Qt. tote. I can use smaller filters to clean the air into the box. Positive outflow of atmosphere the way I am thinking of doing. Further, I think I can mitigate the noise of the fan by isolation. I'm excited. I'm working with a 6' x 12' lab space.

[@nachmanedes9460]

Solid video, thank you, Brother!!

[@OneEarthMushrooms]

Thank you! Happy you liked it!

[@nk-yy3ki]

Very helpful, thank you for this bro.

[@mike_lives]

Great explanation!

[@SincerelySpiders]

You have really neat handwriting…. 😂 thanks for taking the time and explains this! Makes a lot more sense now

[@johnholt-music]

Thank you for this! Just fell into the opportunity to get a Terra Universal Laminar Flow Hood. Had to take it!

[@OneEarthMushrooms]

Heck yeah! Have you had a chance to use it yet?

[@colleenstilley9169]

I got one from MidWest. Initially I was really bummed. I had the little hood (plenty big enough for me) in my cannabis grow room with moisture everywhere and the floor always dirty and muddy. Was running 40 % contamination (at least!) with still air box. Never considered that using the laminar flow in a dirty room and storing your work there would not work. lol....anyway, I moved the hood to a "clean room" and I have had NO contamination doing about 50 grain spawns to quarts/pints a week. None. Very, very happy. I often will run it just to clean the air during the day or night. I know that will cut the life of the filter, but for the price, I believe it worth it...? Thanks for all your great videos. Thank God the price is coming down for decent 97% ones.

[@scotiscoti]

Yes I did learn something thank you

[@orangebetsy]

Good drawings!

[@JayP7.62]

I'm very new. Been doing research on the subject off and on for years but two months ago just started actual trying it out. So far I love it! I use a SAB. After giving agar a try and experiencing some contamination, I did what another guy did on a video here on KZbin. I covered the holes with a really strong and thick duct tape and cut an X in it. Pretty much closes when I pull my arm out and kind of acts like a seal when my arm is in. Also instead of using ISO to sterilize the inside I switched to 10% to 15% bleach water spray. That let's me flame sterilize in the box as before I would do it outside the SAB. Didn't want to blow it up you know lol. I still turn off all fans and home AC about an hour or more before I load the SAB, the spray the inside down really good with a fine mist of bleach water, wait about 30 minutes, then put some gloves on and because bleach takes more time to kill contamination I go ahead and use ISO to spray down my arms and gloved hands and get to work. So far after doing the tape and switching to bleach water I've had no contamination. But I know its not perfect and expect I'll still get contamination every now and then. But it will work until I can afford a flow hood.

[@OneEarthMushrooms]

I still haven't bought a flow hood, they're so expensive. Yeah, an exploding SAB would be terrible! Sounds like you have a pretty good system worked out, I'm betting it works better than mine, I don't use anything to seal the gap between my arms and the SAB. Contam rates are pretty low, but I'm sure I could cut it even more.

[@raytry69]

Hydrogen peroxide could be an another alternative for sterilizing surfaces. Ozone could be for the whole room before do sterile work.

[@ednadeau7384]

Very interesting thanks,, velocity . . .

[@zannxking4128]

1st! ....as always brother, another topic youve scienced the heck out of :D....love it. not had the opportunity to make a LFH myself yet. I've got reasonable aseptic technique and so haven't had the need. However when I soon start to use agar/petri systems it will likely become necessary. Iv used HEPA filters for my gas exchange holes on tubs, but cos they're so damn expensive I just bought a single dupont tyvek suit and started using cuttings from that. I wonder if that material could also be used in a LFH....hmm... will look into all this when the time comes. Peace and mush love

[@OneEarthMushrooms]

Yeah, I definitely recommend using the painting suits. I've seen some people recommend the mailing envelopes that you can get for free from the post office in the US, but honestly that's kind of illegal and not the best use of our tax dollars. I haven't done much agar work, but the 10 or so agar dishes I have going right now did great in the still air box, zero contamination and it's been over a month. Thanks for the first comment! You seem to always catch the videos as soon as they come out! Love you man, thanks as always for your detailed comments and ideas!

[@Stephen_Eee]

Doing a lot of work under a fume hood, I'm SO glad I watched because I was using the same line of thinking, and could not figure out how Sucking air over my work area would be better. Blowing,😂 OMG I'm defintely blonde and those stereotypes are true. Thanks for the break-down

[@Keifefromtwitchtv]

Thank you

[@Gayndhi]

cool video, thumps up. i initially wanted to go for a flowhood aswell, but i am going to make a flow box (?) if you call it like that. it uses one of the thinner air cleaning filters, still a hepa h13 with the same rate of 99.95% as the big ones but way cheaper. and to combat the turbulent air its has walls around it, on top and the left and right, so the air is forced to travel relatively straight and that should limit turbulent air aswell. once its all built i am going to run tests with agar exposing it for 30sec to see how many contam dots it will have, if any. on the internet i read quite some good reports about this setup, but also a lot of people with their fancy 2000$ flowhoods being buthurt that this 100$ design works just as good.

[@MoltenSamurai]

Heh, I'm about to try this out too. Hope it worked out for ya

[@denvermiller6176]

I noticed in your video at :11 you're using some sort of rod to push a hole into the center of your spawn jar. I'm guessing that helps during the inoculation process. Have you experience any issues doing it this way. I love the idea and I'm wondering if there's any risk of additional contamination. Thank you for sharing this content!

[@steffondavis1102]

Hey man, I use a still air box aswell, I sized mines a little too small I find it hard to work inside at times and I offend have spills when trying to pour agar, I am working of building either a larger still air box or laminar flow hood, this video helped me understand alot thanks soo much.

[@OneEarthMushrooms]

You're welcome, and thank you! Yeah, my SAB is a little bit short and I have problem with that from time to time. I put a short clip in the beginning of this video where I was trying to make holes in the center of jars with a rod...I had to tilt the jars sideways to get the rod in. Not a huge inconvenience, but a flow hood would definitely have made that easier.

[@otacon1024]

Oh boy, don't even want to think about what a pain in the ass pouring hot agar inside a SAB is... Even doing simpler stuff like inoculation can be annoying depending on the size. Do yourself a favor and get some reusable (glass or polypropylene) petri dishes that can survive pressure cooking. Pre-pour in open air, PC, wait for them to cool down and solidify - easy mode.

[@everythingis2495]

Put a cheepo eBay negative ion generator in your still air box. You can blow smoke in it to see how it works. Within seconds the air Is totally clean. The neg ions charge particles in the air and since the box is positively charged, the particles stick to the walls. As long as you Lysol the walls it keep those clean, you’re good there but all the air in the box should be completely free of any particles down to the sub-micron . Any Particles attempting to enter the box through any air gaps will immediately stick to the walls before getting much of a change getting in. . I used one in my glove box and never had contamination..

[@SirBrassknuckles]

I love the way you teach things! do you have a video on how to make a laminar flow hood from scratch? What pieces/components to buy and from where, and a step by step assembly method?

[@dominicmorgenthaler367]

I personally like this guys idea: kzbin.info/www/bejne/hHXHmYWvq9V4n9U

[@OneEarthMushrooms]

I don't have a video on that, but I'll add it to my list!

[@__-pl3jg]

There are now some pretty sweet all in one blower/filter units available on Amazon for $500. Thats the same price in materials alone if I built my own. And they're 24"x24" with aluminum bodies and carry handles. Its amazing how many mycology resources have become available within the last 10yrs! Both education and materials.

[@OneEarthMushrooms]

I agree! Pretty great how information is being shared and the resources that are becoming available for the average grower!

[@khawass]

Thx for the info. One question please: how deep shall the plenum box be? Is it important?

[@11macatak]

🙌🙌

[@me.1475]

great video! What are your thoughts on using Fan/Filter units from cleanrooms instead? I know they provide "uniform" and not true laminar air flow but so many people use them I ended up getting one. So far I've been having some issues. I believe now after watching your video that I had my flow rate way too high at first causing air turbulence, so I purchased an Ananometer and sett it much slower in speed, I've also built a 20" containment unit out of 1/4" acrylic glass around it on all sides, and have moved it away from the wall in hopes of achieving Laminar flow or at least a suitable contaminant free environment, do you think this will be suffice or should I have just build a damn flow hood myself to begin with? Thanks!

[@Barbie.Boo1961]

Wow. That’s a lot. I think I have wasted my $ on mono tubs and grain, and spores. I don’t have any of these things

[@elmussom5433]

Hi. How to calculate if a certain filter will create a laminar flow and under what airflow parameters will it happen?

[@apriljames726]

I'm going to try a Winex C545 With Plasma, PlasmaWave® air purifier technology creates a short electrical discharge to create dual polarity ions from air moisture that are dispersed into the air. this might be the same as a laminar flow if turned to lowest power pr. Still working out the math~*~ . I already have this air purifier It has a HEPA filter, Charcoal filter, and Plasma flow. So I was thinking if I used it back wards it would work like a flow hood. I am working the numbers and I believe it will work. Going to get some agar and test in Front of the Winex C545 Backwards and see if it docent work. The Plasma wave seems to me dose the same as a Laminar air flow hood would do. I could be wrong Just Thinking mathematically these are the same. Haven't figured the math out yet but seems to me it would work the same. The Rookies Rookie so not sure Testing my hypothesis. Any one have thoughts on Plasma wave and Laminar flow?

[@sauroman1]

Can it be made from air purifier such as BAP412?

[@mitchlee5385]

Car cabin filters are HEPA standard with 99.97% filtration capacity at 0.3 microns. I’m wondering if a laminar flow can be created through one of these inexpensive filters with a computer fan. If so, the DIY cost of a laminar flow hood/cabinet with HEPA standard air filtration would be less than $80.

[@OneEarthMushrooms]

Worth a shot, thats pretty cheap!

[@iz4485]

Using an anemometer what readings should I expect from a laminar flow hood

[@MysteryMycology]

Only a hotwire anemometer is appropriate, but 90 fpm+/-10 fpm at 12 inches from the face of the filter, with all values within 20% of the average.

[@zerosyn6035]

im getting into agar. what if i wasnt able to do the carpentry and didnt have the space for a full box/hood to make a laminar flow hood, and decided to use a BOX FAN behind the HEPA FILTER and that's it. will that work???

[@3dp_edc]

you wont get laminar flow but it MIGHT work if your working close enough to the filter. key word there MIGHT.

[@AlaskaMycophile]

Myco Willie builds one on KZbin. Honestly, though I haven't compared, I'd feel safer in a SAB than a box fan with HEPA filter

[@MrFurley69]

Currently a nice still closet

[@OneEarthMushrooms]

Haha! Yeah, I still haven't upgraded to anything this fancy.

[@defqon555]

How do u store the box when not using it, or prevent it self to not get contaminated? Spray it with alcohol before every use?

[@OneEarthMushrooms]

I personally do not own a laminar flow hood, so I dont have any personal experience to speak of. I think that covering the flow hood to prevent excessive contamination of the filter elements would be sufficient. If anyone else has experience, feel free to chime in!

[@danielche2349]

What’s the difference between fluid viscosity and fluid density?

[@OneEarthMushrooms]

Viscosity describes a fluids resistance to flow. Imagine a thick fluid, like molasses, flowing down a hill. Compare that against water, which is less viscous. The water will flow more easily than the molasses. Density describes the amount of molecules in a given volume. Haha I like to think of it like balls in a box....the balls represent the molecules and the box is the "given volume". The more balls I put in the box, the more densely packed the box is, and the more that box of balls will weigh....i.e. density goes up. Hope that helps!

[@danielche2349]

OneEarth Mushrooms gotcha, thanks!

[@OneEarthMushrooms]

@@danielche2349 you're welcome!

[@Dammy1998]

Will an Air Purifier work as a LFH?

[@3dp_edc]

Actually, its not the thickness of the filter that really matters its the resistance the filter gives. If its not enough resistance, there wouldn't be enough back pressure on the filter. Mine is built with a 3" hepa. and works fine. Many other creditable sources also use 3" thick filters for their build guide for example on this build here, one of the most referred to builds when people ask how to build one on the forum site I'm on for mushroom growing.

[@OneEarthMushrooms]

Good to know!

[@fighttilltheendfighting6819]

hope u made a vid about monotub xD

[@OneEarthMushrooms]

I'm actually planning out a while series for monotubs right now! I want to go into detail about every step, because people have so many questions about the steps of using a monotub.

[@svgs650r]

Great vid, just one problem...you've not built a laminar "flow-hood" or more properly a Laminar Flow Clean Bench because w/o a discharge duct it's not a "hood", and w/o a discharge duct your laminar flow air column breaks down rapidly entraining non-filtered air and risking contamination of your culture medium Google a Laminar Flow Clean Bench which is what you're actually trying to build and you'll notice the difference immediately. There is a reason all the manufactures Laminar Flow Clean Benches look and perform the way they do and that's because that's the way they have to look in order to perform the task in which they were designed. Add a discharge duct, cardboard and duct tape are your friend

[@AlaskaMycophile]

Fuckin A. That's the difference between a handgrenade and an atom bomb. Without The Cave,as I call it, you're flirting with disaster unless you're right up the flows ass

[@douglundy]

nice simple explanation but Id contest your assertion the filter sorts the air into laminar flow. Its just the design of the box with the speed...yes the resistance probably helps but a wind tunnel has no filter and its also laminar. I built one with a 325 cfm room air filter with all the parts this has and it blows about 300 cfm. You havent clarified why this 'bad' flow hood fails to have laminar flow..

[@agravy7657]

Never seen a vid with 0 dislikes before

[@OneEarthMushrooms]

Haha don't jinx it!

[@63phillip]

I use UVC light to sterilize my small room and all my equipment and substrate .

[@dustinmoore1559]

I was looking in to one of those. How well is it working?

[@63phillip]

@@dustinmoore1559 No contamination yet, just the ozone smells bad after use. just remember do not use it on live cultures. And make sure you get a real UVC, lots of fake ones on the market some dangerous ones. Read up on UVC usage before using it as it can cause damage to humans and plants.

[@earthenaaron6766]

For those of you looking for a place to find filters, i finally found a place! i got a 24x48 size filter with all the reqs off of www.hepaflow.org/ hope this helps!

[@coolcat6149]

Question, I have a dyson air purifier/fan would that work? 😂

[@middleway1885]

Boop! Science! Lol

[@Typhus-th6ud]

I'm an airbrush artist so I literally just need to reverse the flow on my spray booth

[@OneEarthMushrooms]

Nice! Thats handy.

[@JasonAlexzander1q47]

Willy Myco has an hour long video on building one that is 24" wide 12" tall and 24" deep. However I'm wondering if a person were to build a pre-filter box around the blower fan. If they would need a more powerful blower than what is used on the video? So that proper laminar air flow is still achieved? Thoughts?