The smallest harmful particle when soldering with flux is 3 times smaller than this filter can. MERV 20 or ULPA filter to get this particle size. Anyone who tells you otherwise will lose $ in the industry (employee health, factory cleanup, filter sales, etc.). The lid does not fit perfectly (still seals the filter). The fan is small and quite loud at high speeds. The price is painful. And yet we keep it! Here's why: there isn't enough competition in this space and it keeps prices high, nothing can be done about it until more people want to do it. Outside. We can't hear the fan, and the HEPA filter doesn't give you a false sense of security because it's outside in a locked drawer. The filter is designed to capture vapors before they are released into the outside air. (If you are outside our lab and hear the fan running, do not stand near the box that says WARNING: DO NOT STAND HERE) The included 2 3/8 inch diameter hose is great! It is very flexible and durable. We routed this hose through the wall to the outdoor unit. The 2.5 inch hole saw is perfect for the job. The fan is powerful and sucks in fumes like a junkie. just need another hose). The size is very good, many of them fit in a small space. You can turn it on with a simple switch - so we've connected an "Alexa device" and now activate it with your voice. Replacement filters under $100 for a HEPA filter and $15 for a pre-filter - not bad! Spare parts available. a true ULPA filtration system that costs less. Soon. not yet :(