“Clean” rooms are places to work with controlled temperature, humidity, and most importantly limited small particles – stuff like dirt, dust, smoke, hair and clothing fibers, bits of skin, little pieces of anything that crumbles as it decays. The outside air entering a cleanroom is cleaned up with the filters system. The new air travels down the room, pushing the contaminated air to exit through return air intakes at the bottom of a special space in wall. This ongoing process keeps the environment in cleanroom.

For the most part clean rooms are to protect things like computer or other electronic devices (chips). These have conductors that are closer together than the size of dust particles, commonly a fraction of a micron, and tiny particles can cause a short circuit, just like your dropping a metal knife into a toaster; it makes a path between conductive elements and so causes the “short”.  Another use of clean rooms is to keep optics free of contaminants – here we worry about smoke or tiny droplets that can settle on or dry on optics. At ECL, we use exotic detector chips called MKIDs which have conductors that are micron-size structures, and we also assemble and test optics.