DIY clean box

Working with micro organisms requires sterile (or almost) conditions, to keep cultures pure and prevent infections. When working with culture media it is especially crucial to do it with great care. This can be done very simply, by using a bunsen burner and working in a small radius around it. This is not very practical when working with many plates, however, as the radius of the “clean zone” is relatively small.

Therefore professional labs use so-called clean benches or laminar flow hoods, which have a defined air filtering and circulation system, making sure only clean air comes into contact with the sample material. Commercial clean benches are quite expensive, but one can improvise a simpler solution, as did we. The construction is very simple, a big plastic box was used as the base and then a large opening was cut out on the side, to enable handling of materials and two small holes were cut on top, and old server fans were used for air blowing and filters were installed. Usually HEPA (High-efficiency particulate arrestance) filters are quite expensive, however, new generation vacuum cleaner bags, suitable for alergics (presumably filter spores and bacteria) can be used as well. A plexiglas cover was used to close the box when not currently in use and voila! Finished is the “clean box”.

To test if it actually allows for sterile work, LB agar (unspecific medium for bacterial growth) was prepared into 3 sterile petri dishes and left open in a running box for 72 hours. After the time has passed, the petri dishes were evaluated and we were very happy to see no bacterial culture has grown on the media, meaning the box is suitable for microbiological work. It is still not ideal yet and an upgrade is planned with a perforated floor plate and air suction for actual flow control.