Still Air Box vs Flow Hood: Which Is Better for Mushroom Growing?

Still Air Box vs Flow Hood: Which Is Better for Mushroom Growing?

When it comes to clean work in mushroom growing—whether you’re pouring agar, making liquid culture, or transferring grain—two tools always come up: the still air box (SAB) and the flow hood.

But do you really need both? Here’s an honest breakdown from years of hands-on experience.

🧰 What Is a Still Air Box?

A still air box is simply a big clear tote with arm holes cut into the sides. It works by blocking airflow and letting contaminants settle, giving you a calm space to work. No fancy filters or fans—just still air.

I’ve mainly used a still air box for years and have very high success rates. You can make one cheap or even buy a pre-made version online. My setup is basic, but it works.

My SAB tips:

• Turn off your AC or fan, and close any open windows before starting.

• Wipe the inside of the box with 70% isopropyl alcohol (not 90%). 70% kills bacteria better because it evaporates slower.

• I used to spray Lysol inside, but stopped—and my success rates stayed the same.

• I also used to wear gloves but don’t anymore. Now I just wash my hands thoroughly, then wipe them with rubbing alcohol before working.

• Let the alcohol evaporate for a minute before opening jars or plates.

Simple, cheap, and reliable. If you’re on a budget, this method will take you far.

💨 What Is a Flow Hood?

A flow hood uses a HEPA filter and fan to blow clean air across your workspace, pushing contaminants away from your plates or jars.

They’re ideal for serious growers who do a lot of agar work or grain-to-grain transfers. But they’re expensive—commercial models can run hundreds of dollars.

That said, a lot of growers (including me) experiment with DIY flow hoods. My plan this fall or winter is to make one using a box fan with filters on the front and back. It won’t be perfect laminar flow like a real lab setup, but it’ll still filter out a ton of airborne dust and spores. I’ll document that build in a future post.

⚖️ Which One Should You Use?

If you’re just starting out or doing small batches, a still air box is more than enough.
If you’re expanding to bulk spawn, doing constant transfers, or selling cultures, a flow hood becomes worth it.

My take: Start with a SAB. Get good at your sterile technique. When your success rate is solid and your grows are consistent, then move up to a flow hood.

🧴 Recommended Tools

• pre-made still air box

• 70% isopropyl alcohol

• Nitrile gloves (optional)

• Flow hood premade

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📗 Ebook

Want the full sterile workflow from agar to substrate?
Grab my ebook “Mushroom Recipes for Cultivation” — it includes step-by-step guides for agar, liquid culture, and substrate recipes.