At some point in the career of every aspiring mycologist, a phase is reached where they want to go beyond basic growkits and cultivation practices. They want to make grain spawn, work with agar, clone mushrooms, germinate spores, or simply reduce their rates of contamination.
This is where Still Air Boxes and Flow Hoods generally enter the picture. These tools allow growers to work in a controlled environment where contamination can be significantly reduced or eliminated. They are absolutely necessary for many of the advanced techniques used in mushroom growing. They make up the “heart” of any laboratory, be it a professional-grade lab, or a DIY home lab you prop up in the corner of a spare bedroom.
Why Do You Need A Flow Hood or Still Air Box?
Microorganisms are ubiquitous in the environment. They’re on almost every surface, including your skin and clothing. They’re also in the air we breathe and that which we exhale, and have even been found high up in the atmosphere.
These microorganisms, usually in the form of bacteria or molds, can become a source of contamination in mushroom cultivation. They do this by not only competing with your fungus for food resources, but can also act as direct predators. Many contaminants also release cocktails of growth-inhibiting compounds, which prevent the development of mycelium in a substrate.
Many people wonder why it is that mushroom cultivation requires so much sterility when, in fact, mushrooms appear in the wild with no human intervention at all. The answer to this is complex but comes down to the fact that every fungus is specifically adapted to very particular ecological conditions.
When we isolate a fungus and attempt to culture it, there are tons of “weedy” microorganisms that can outcompete it. This is especially true when we talk about nutrient-rich substrates like sterilized grains or agar, where these other microorganisms thrive.
Flow Hoods and Still Air Boxes: The Difference
Still Air Boxes and Flow Hoods are tools utilized to create the sterile work environment needed in various processes of mushroom cultivation. While there are many ways to grow mushrooms without them, they become crucial for growers attempting more advanced processes like culture work or spawn production.
While both flowhoods and still air boxes are effective at what they do, it’s not exactly a fair comparison. Generally speaking, flow hoods are considered superior pieces of equipment that are easier to work with and offer more versatility. The downside to them is the cost and the physical space which they take up, both things that make Still Air Boxes an attractive option for hobbyists.
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Still Air Boxes are enclosed containers (often a large clear plastic bin) with two armholes aimed at creating still and controlled environment inside it. The concept is that when the air is still, particulates and contaminants settle to the bottom and are no longer floating in the air, where they could land on your sterile materials. The two arm holes allow for access and, with very careful and intentional movements, enable you to manipulate your sterile materials and culture. Precautions like disinfecting all surfaces and materials, aswell as working in a sealed room can help improve these results.
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Benefits: The most significant advantage of Still Air Boxes is that they are cheap, portable, and can be used almost anywhere. Also, they are effective when used properly. You can easily make or purchase one for under $40. Despite generally being considered inferior to flow hoods, they are practical and preferred by some growers. The fact that you can easily pack it away is also great for someone who doesn’t have a permanent laboratory setup.
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Drawbacks: The downsides are that they can be more challenging to work with and uncomfortable, especially if you are doing a lot of sterile work. They can feel clunky and restricted, and first-timers can quickly challenge their technique. They are also usually limited in size, meaning that specific processes, like inoculating large grow bags, can be complicated.
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Best Suited For: Hobby growers and amateurs on a budget. Whether you want to make grain spawn or isolate the Oyster mushroom you found in your backyard, a Still Air Box can do the job. It’s also lightweight and easy to move, making it convenient for storage. Generally speaking, they would be considered a “first step” for aspiring mycologists.
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Flow Hoods are essentially devices that blow highly filtered air in a single direction over your workspace. By working under this “shield” of highly filtered air, you can effectively prevent exposing your plates, grains, liquid cultures, and tools to contamination. The hood is composed of a fan and a HEPA filter, which is effective at removing more than 99% of particulates. Some times flowhoods are oriented vertically, with filtered air blowing downwards onto your work table, while other times they have horizontal orientation. The latter is what you most typically see from most growers and small-laboratories. Flow Hoods also rely on the principle of laminar flow, which means that the air is moving in a single direction free of any turbulence. Turbulence can create wind currents that pull in contaminated air outside the range of the HEPA filter.
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Benefits: Provides ample workspace and comfort for sterile work. This means you can have your tools and materials spread on the table, and move your hands without constraints. It allows you to work faster as there is no need to wait for the air to settle. The learning curve might be a bit lower than a still air box. They come in many sizes and are very effective alongside sterile techniques.
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Drawbacks: Flow Hoods are expensive. Prices generally start at $400 for a simply used flow hood and easily reach prices above $2000 new. It can be well worth it to build your own if you're on a budget. They may also require maintenance and the replacement of the HEPA filter.
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Best Suited For: Professionals, market growers, and serious hobbyists.
Don’t Forget... Sterile Technique Is Always Needed
It’s crucial to understand that while equipment is essential, it does not make up for bad technique. You can have the best flow hood in the market, and if your technique is flawed, you’ll still suffer from contamination issues. Likewise, if you have a homemade still air box and utilize flawless technique, then you can avoid contamination altogether. While both Flowhoods and Still Air Boxes require sterile workflow, it’s good to emphasize that this looks a bit different in each.
Conclusion
Chances are, if you're considering between the two, your best option might be to start with a Still Air Box. They’re cheap to make or buy, so there’s little to lose in the investment. They will help you get used to the sterile workflow and serve as excellent practice if you ever decide to go with the laminar flow hood. Unless you’re thinking of starting a significant operation, Still Air Boxes are usually all a hobby grower needs.
