Every contamination in a sealed bag arrived on a particle in the air. The two tools growers use to keep those particles out of open bags and plates take opposite approaches. A still air box stops the air moving, so nothing falls into your work. A laminar flow hood pushes HEPA-filtered air across the bench, so anything that would fall is blown away. You need one of them for any step where a bag or plate is open: spawning to substrate, agar transfers, grain-to-grain. You do not need either for a port injection with a flamed needle.

The still air box

A clear plastic storage tub, 50 to 70 litres, turned upside down or used on its side, with two arm holes cut in the front. You put everything inside, spray it with 70% alcohol, let the air settle for a minute, and work with slow, low movements. Because the air inside is still, airborne spores settle onto surfaces rather than into your open bag, and because your arms enter through holes rather than lifting a lid, you do not stir it up. It is the tool that made home mycology possible and it costs the price of a tub.

1. Pick a tub

   Clear, so you can see your hands. 50 to 70 litres is roomy; 35 is workable.

2. Cut two holes

   10 to 12cm diameter, 25 to 30cm apart, level with your forearms when the tub sits on the bench. A hole saw and a drill, or a heated can rim pressed into the plastic. Sand the edges.

3. Prepare

   Spray the inside, the bench and everything going in. Gloves on, sprayed. Wait a minute.

4. Work slowly

   No sudden movements, no talking over the work, no withdrawing your arms mid-transfer. Lids and bag tops open for seconds.

The flow hood

A box with a fan pulling room air through a pre-filter and then a HEPA filter rated to remove 99.99% of particles at 0.3 microns, delivering a smooth, laminar sheet of clean air across an open-fronted work area. You work in that air stream, with the open bag or plate upstream of your hands, and contaminants never reach it. Agar work in a flow hood is fast and relaxed; grain-to-grain becomes routine. Hoods cost from several hundred dollars for a small bench unit to a couple of thousand for a large one, or a few hundred in parts if you build one.

Which one, when

• Your first year: a still air box. It teaches the slow, deliberate habits that make you clean anywhere.
• A few grows a season: still air box. Spawning a 5kg tub is the only awkward job; do it in stages.
• Regular agar work or many bags: a flow hood pays for itself in saved cultures within a season.
• Both: many growers keep the SAB for one-off jobs and use the hood for batch work.

What neither replaces

Clean air does not clean a dirty tool. Flame scalpels and needles, spray gloves, wipe ports, keep lids closed, and work with things that were sterile to begin with: a sealed grain bag, a pre-poured plate, a substrate bag opened for the first time inside the box. The air tool is the last layer, not the first.

Written by the Aus Myco Kingdom crew. Everything here is general growing information for gourmet and medicinal species; your room, your climate and your culture will have the final say.