Many States have implemented law by the DEC,that Dental Offices are required to install a Amalgam Separations  Filter System  prior to their central vacuum system to eliminate the mercury from being discharged into the enviroment waste water. You should check with your State DEC to see when the deadline to have these installed is,,,,,these systems are very easy to install and any Do It Yourselfer can do it,,all the systems available have a collection filter system that meet or exceed the minimal filtration rate set by the codes. However,,there are a couple things you should look for when deciding on which system to get,,,their are systems you could put in for each operatory versus central systems for entire office,,individual operatory system can be very costly  as the filter has to be changed  every 3 months based on a single Doctor use and most offices have 2-3 operatories,,,,Systems that are centrally installed at the central vac can handle anywhere from 8-12 operatories and the filters have to be changed every 12 months to every 18 months,based on a single doctors use,,depending on manufactures recommendations,and the code states that you must replace according to manufactures recommendations,,if 2 doctors are working full-time,then the recommended replacement times are cut in half,,all replacement collection cannisters come with the cost of recycling included in refill cost,,systems are pretty much the same price range for initial start up,,however refills would become more costly depending on recommended replacement times,,,I have found that one system on the market when filter becomes full or plugs up, you will notice your suction will diminish very rapidly and you had better have a replacement filter section available for this some what self contained system,where as another system has a  seperate collection filter assembly and if it becomes full or plugged you can still operate without suction loss,,any questions,,feel free to contact me,,,thank you