Still Air: How to Work Clean Without a Laminar Flow Hood

You do not need a laboratory. You need dead-calm air, a wiped-down surface and a sense of what not to breathe over an open jar.

What still air is, and why it is the whole trick

Contamination in home growing is mostly falling spores and dust carried on moving air. A laminar flow hood beats that with a wall of filtered air. A still air box beats it by simply having no moving air at all, and for the scale most people work at – jars, bags, a bucket of grain – a clear plastic box with armholes is honest engineering rather than a compromise.

The alternative is a bathroom after a hot shower with the door closed: the steam drops the airborne particles to the floor for about half an hour. It is not a sterilisation method, it is a still-air method, and it is free. Wait for the surfaces to stop streaming before you work, or you will waterlog your grain.

The setup, in the order that works

1. Close the room. Windows shut, extractor off, fans off, pets elsewhere.
2. Wipe the work surface and your forearms with 70 % isopropyl and let it flash off – alcohol works wet, not as a smell.
3. Flame the neck of a jar or the blade of a scalpel only if you are experienced enough to not panic when the alcohol runs. Otherwise skip flames entirely and rely on still air.
4. Everything open stays in the box: jar lids off, bags rolled open, spoons inside. Nothing goes in and out of the box while a container is open.
5. Work quickly and boringly. The exposure time is what you are minimising, not the tidiness of the bench.

A simple grain-to-bag workflow

Break up a colonised jar in still air, tipping it rather than scraping it with anything that has been on the bench. Pitch roughly a tenth of the wet substrate weight, more if the grain is slow or the bag is cold. Mix without opening the bag wider than your fist will fit through – most home bags are contaminated at the fold, not in the middle.

Seal with micropore tape so gas moves and spores do not. A patch on the top face, never buried in wet substrate. Then leave it alone in the dark at the temperature on the species listing, and check it once a day rather than four times.

If you only learn one judgement call, learn this one: a colonising bag that is 20 % white and stable is going well. A bag with dry, fluffy white growth on the surface of the grain while the substrate beneath stays brown and smells sweet is usually fine. A wet, discoloured, sour patch is done – bag it and take it outside.

What is actually worth buying

• A still air box – the highest return per dollar in the whole catalogue.
• 70 % alcohol and paper towels – not 91 %, which evaporates before it has worked.
• Micropore tape – because packing tape on a filter bag is a mould incubator.
• A scalpel with replaceable blades – a dull blade slips and tears plastic, which is a hole you will not see until day six.
• A thermometer-hygrometer – so that arguments with your own setup are settled with numbers.

Skip for now: laminar flow carts, agar plates, polysorbate, a second pressure cooker. Learn one cycle in still air, then add equipment for the specific problem it showed you.

The short version

1. Close the room; stop all air movement. Still the air
2. Wipe surfaces and hands with 70% isopropyl; let it flash off. Wipe down
3. Keep every open container inside the box, lid on before you step away. Work inside the box
4. Seal with micropore tape, incubate dark, check once daily. Seal and wait

Kit list for this guide

GROWING SUPPLYStill Air Box, Clear 66 L$34.00GROWING SUPPLYCultivation Tool Set: Scalpel, Sprayer and Gloves$28.00GROWING SUPPLYFilter Patches and Micropore Tape Bundle$22.00

Written by the MycoGrow fruiting room. No claim here guarantees a harvest: a grow is a living thing in a room you control, and the room is the variable.