A laminar flow hood is a large HEPA filter connected to a ventilation fan. There is an air chamber box built around the HEPA filter and the fan is mounted on top of the box. The fan pushes air through the air chamber and out of the HEPA filter creating 99.99% clean air for you to work in front of. A laminar flow hood is very effective at eliminating contamination as you do your mycological work, and is much easier to work with than a still air box. We do all of our work in front of a flow hood.