Positive pressure boxes, Box fan flowhoods, Gloveboxes, and Automated Mono-Tubs.

Plenty of new folks have questions regarding equipment, their application and efficacy. From YouTube influencers, sub reddits, Facebook and Instagram, there's no shortage of encouragement regarding these devices; let's take a moment to talk about these contraptions.

First:

Can one produce clean cultures while using any of the contraptions covered by this post? absolutely!

Cultivators with little to no experience can produce clean cultures in the open air without a box-fan flowhood, positive pressure box, shmuvbox, clean bench, SAB, or any other known cultivation tool. Humans have been growing mushrooms for thousands of years.

One can produce clean germination plates by shooting or streaking multispore solution onto agar; clean spawn can be produced by spraying MS-solution liberally over cereal grains. It's incredibly easy to produce cultures or spawn, and by extension to grow mushrooms; anything can be achieved with a little luck.

We're not operating in a CDC clean room environment with virulent/pathogenic viruses or bacteria, cultivators can get away with an awful lot of shenanigans on a small enough scale.

Can you produce mushrooms while using a: shmuvbox, positive pressure box, boxfan flowhood, glovebox, etc? Yes! Everything "works" so long as you possess the appropriate genetic starting materials like spores, or live mycelium, and a substrate upon which they will grow.

Cubensis will grow on manure, cigarette butts, bibles, fancy underwear, rags, etc. Just because you can, doesn't mean you should.

The topic of this thread covers the usage and theory relating to equipment employed by cultivators, not the statistical probability for rates of contamination while using them. Having said that, the statistical probability of failure is much higher while employing incorrect equipment or techniques.


Let's start with the appropriate equipment first, once those are explained things will make more sense when we cover the fundamental flaws of the others.

Laminar Flowhood/Fan Filter Unit (FFU)




A laminar flow bench, Bio safety cabinet, or FFU (fan filter unit) utilizes velocity and geometry to force air currents into ordered lamina through a filter designed to efficiently remove particulate to at least .3 microns. These filters are specifically designed for laminar flow applications.

Laminar flow units are calibrated to produce a flow rate of 90-110 feet/min evenly across the entire face of the filter. This velocity will ensure stable flow without transitioning to turbulent flow.



This lamina has been arranged by the resistance generated by the HEPA filter (static pressure), the internal geometry of the filter, and the volumetric output of the blower. The blower has been matched precisely to the surface area of the filter face, and to the filters resistance/flow rate @ 90-100fpm; this combination allows for sterile, turbulence free air to flow over your work area.

The turbulence generated by objects in flow (including your hands and tools) have the potential to pick up microscopic contaminant particles from your hands, etc, and then deposit those particles into your work if you do not have great technique. Needless to say, these particles will produce mold.

Attention to detail is important when working with microorganisms, sterile work not only requires sterile media but proper maintenance of that sterility by minimizing exposure to potential contamination while working. Plan ahead of time where to place objects in flow; plan how you expect to move, where to place utensils and how not to produce unnecessary turbulence by crowding your work area, or by placing objects between the filter face and your work while moving.




Still Air Box

A still air box on the otherhand is an enclosed area that allows for particles to settle via gravity due to the absence of turbulent air currents that would otherwise keep them aloft, this is why they're called a "still air box".

Slow calculated movements are required to prevent turbulence which will carry contamination into your work.



This shows the time to settle in still air from a height of 1.5m; allow ample time for particles to settle in your still air environment.

Household dust typically consists of some combination of: human skin flakes, animal fur, decomposing insect parts, food debris, lint and fibers from clothes, bedding, and other fabrics; tracked-in soil, soot and ash, particulate matter from smoking and cooking, allergens and pollutants from the environment. Your climate and geography will affect the composition of household dust.

When operating your SAB: Turn off fans, AC or furnace ducts that disturb air currents within your space. Don't place speakers on top of your SAB, don't bang your SAB, don't place warm lights in contact with the top of your SAB.

Keep your work elevated off the floor of the box where the contaminant particles will settle; do not spray isopropyl alcohol inside of your box, do not flame sterilize instruments inside of your box.....don't disturb the air within the 'SAB' at all, up to and including pumping air directly into your SAB (filtered or not).

Use a SAB if you do not have an appropriate flow cabinet/FFU!


Glove Box



By securing gloves to the opening of your box you will be creating a vortex type turbulence within the box:

Gloveboxes create vortex type turbulence within an enclosed space, the frequency and amplitude of that turbulence is far greater than that of external air currents that interact with a standard SAB.

Don't make a glovebox:

"A glove box is a sealed container used to manipulate materials where a separate atmosphere is desired. They are commonly used to protect workers from hazardous materials or to protect chemicals and materials that may be sensitive to air or water vapor"

Glove boxes are not suited for microbiology, do not attempt to build or use one of these for cultivation.


Positive Pressure Box



As you can see these are SAB' outfitted with fans, the addition of fans will create a turbulent air box.

Positive pressure implies airflow into an enclosed area which means this air regime will by definition become turbulent flow due to the geometry of the ducting and work area. When turbulence is introduced into a system it creates turbulent eddies within the workspace:



These eddies will inevitably move particles (mold spores etc) around and into your work. This is no bueno.

No matter how clean your environment may appear to the naked eye, this is the reality:



Particles are suspended in open air as well as inside of your box. You are covered in particles, you shed particles produced by your skin, your hair, your respiratory system, etc.

SAB' work because you're allowing gravity to settle airborne particles that line the plastic walls, floor, and ceiling of your tub, including any ductwork should you attempt to attach fans; this will remain true even if you were capable of evacuating all particles from the system due to the particles found on your arms, jars, bags, petri dishes, etc.

Introducing any gases, filtered or not, will kick these invisible particles back into the air due to the velocity of the introduced gas and the internal geometry of the box. Any air movement in a confined space will create turbulence/eddies.

Turbulence = contamination, no exceptions!

Not suited for microbiology, do not attempt to build or use one of these for cultivation.


Box Fan Flowhood/budget "flowhoods"



Check out the mold babies this guy created with his "flowhood"

"Gordo tek" is nothing more than a low quality filter matched to an over powered blower. This is not a flowhood:

1 fan + 1 filter doesn't equal anything other than mold.

Why doesn't this "budget flowhood" work? Well, remember that laminar flow is required which is the product of resistance, velocity, and geometry; furthermore the filter is not designed to filter out microscopic particles with high efficiency.

A blower attached to a filter, or set of filters, would be more aptly called a "blowhood". The particle sampling data clearly illustrates how ineffective the standard hardware store filters are when it comes to filtration efficiency.

3 reasons why a boxfan/blowhoods fail to mimic actual clean benches:

1. The velocity produced by a box fan falls well short of the minimum required to produce laminar flow;

2. Hardware store filters are not the sort of filter designed for high efficiency particle filtration, even if they were, not all HEPA filters are designed for laminar flow applications;

3. The filter does not produce enough resistance and does not possess the correct internal geometry to align the airlflow into lamina.

As a result you're left with a turbulent flow machine that sucks in contaminant particles, (maybe the filter catches some of the larger debris like cat hair, etc) but ultimately blows microscopic particulate all over your work area.

Quote:

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Brewtality said:
I have some data to add to this thread.

I am not sure of the tek responsible for proper construction of a "Blowhood", but I went to Homie Depot and picked up the finest ingredients available on the shelf.

1 Lasko (Made in the USA) 20" box fan.
1 Honeywell 20"x20"x1" Elite Allergen Air Filter - FPR10
Roll of tape.

A quick run through the Gargler told me FPR10 is roughly equal to MERV13.

I ran a few tests using a Lighthouse Solair 3100 Particle Counter and these are the results.

This strictly evaluates the potential for contamination based on the number of particles in the air. Organisms that contaminate don't have feet, they don't walk into your plates, they ride on particulate.

The testing and method:
The samples were collected 12" from the filter face.
Each location was sampled 5 times and the results were averaged.
The sample duration was 1 minute.
The sample size was equal to 1 cubic foot of air.
All values represent particles 0.5 microns and larger.

Background Sample: Room Air Sample, no fan running (Aka Baseline)
High: 299,691
Low: 296,907
Average: 298,246 particles per cubic ft

Fan Sample: - Fan running on high with no filter
High: 284,209
Low: 260,840
Average: 270,921 particles per cubic ft

Fan with Filter: Speed setting 3 (High) with Filter attached.(Avg velocity 180 ft/min)
High: 61,895
Low: 29,653
Average: 39,734 particles per cubic ft

Fan with Filter: Speed setting 1 (Low) with filter attached. (Avg velocity 79 ft/min)
High: 20,190
Low: 18,577
Average: 19,571 particles per cubic ft

Chinese FFU Imported and marketed to the mushroom farmer: Speed Setting 3 (Average velocity 63ft/min)
High: 0
Low: 0
Average: 0 particles per cubic ft

The data above shows that using the method I have outlined the box fan filter fails to adequately reduce the particulate load when compared to a proper HEPA filter. You can decide if your time and money are worth the risks.

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Particles sampled using this equipment:

https://www.golighthouse.com/en/airborne-particle-counters/solair-3100

Brewtality certifies clean benches and clean rooms for ISO classification.

Common hardware store filters do not efficiently reduce airborne particle concentrations, they are not designed for laminar flow nor do they produce laminar flow; this class of filters will produce particles. 


Not suited for microbiology, do not attempt to build or use one of these for cultivation.


Automated Mono-Tub

Quote:

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au·to·ma·tion

noun

the use of largely automatic equipment in a system of manufacturing or other production process.

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Mono-tubs are equipment that are used for the production of mushrooms, this equipment, despite lacking electricity or moving parts, is automated. Mono-Tubs are 100% self contained, self sufficient, self regulating, self humidifying, fresh air exchanging environments.



By properly hydrating your substrate and spawning at an appropriate depth you are creating a moist/humid environment, this environment will maintain the appropriate humidity throughout the fruiting cycle providing there isn't excessive air movement within the room you choose to keep them in. No need for fanning, no need for misting.

The holes on the walls of the tub allow for warm air created by your culture to travel up and out of the holes situated at the top of your tub, as well as the gap between your lid (so long as the tubs aren't stacked); as the warm air exits through the top holes fresh air comes in through the holes situated at substrate level. This is passive automation, mono-tubs are designed to not require active automation. The addition of automated humidifiers and fresh air exchangers inhibits the environments ability regulate itself and produce a stable microclimate.

I personally prefer modified tubs, tubs with holes drilled into the ends below the handles and sides above the substrate level for the following reason: they can be stacked without loss of airflow.

Unmodified tubs (tubs without holes) lose airflow when stacked for obvious reasons: the lid gap is closed when stacked which prevents airflow ; )

I have never once saw a tub automated by the addition of some contraption out-perform a dialed mono, and neither have you.

Don't use automated mono-tubs.


UV light's


Ultraviolet germicidal irradiation (UVGI) is a disinfection method that uses short-wavelength ultraviolet (ultraviolet C or UV-C) light to kill or inactivate microorganisms by destroying nucleic acids and disrupting their DNA, leaving them unable to perform vital cellular functions

Ultraviolet lights are 100% unnecessary, this equipment has no application for the production of agar plates, liquid media or spawn.

1. Sterilization is required for media and grain spawn, why attempt to use two methods of sterilization when steam sterilization is the most versatile and effective of the two?

2. UV light cannot penetrate grain, this should be self evident, this is why we utilize autoclaves and pressure cookers;

3. Pressure cookers/autoclaves destroy bacterial endospores, UV does not compare:

Bacillus endospores are 5–50 times more resistant to UV radiation than their corresponding vegetative cells

https://academic.oup.com/femsec/article/51/2/231/503139

4. Agar and other liquid media is sterilized using autoclaves/pressure cookers, it would be pointless to utilize UV to sterilize groups of individually poured petri dishes;

5. UV lights will not sterilize the "air" within a glove box, positive pressure box, SAB, etc.

Ultraviolet lights are pointless, do not attempt to use these tools for the purposes of producing clean cultures.
Steam sterilization is effective and safe., UV is not.

UV has no practical application for  mushroom cultivation.

https://www.ehs.washington.edu/about/latest-news/trouble-uv-light-your-biosafety-cabinet


Ozone

When inhaled, ozone can damage the lungs. Relatively low amounts of ozone can cause chest pain, coughing, shortness of breath and, throat irritation. It may also worsen chronic respiratory diseases such as asthma as well as compromise the ability of the body to fight respiratory infections.

Just don't use ozone, please...smh

Adopting poor habits, using the incorrect tools or procedures does not make you a pioneer or a trailblazer, it makes you a noob.

Use the right tools for the right job, employ the proper procedures and techniques.