General Tools’ Floor Air Filtration System automatically turns on when its infrared sensor identifies particles in the air as small as 1 micron, and then adjusts fan speed depending on the number of particles sensed. The unit has a replaceable interior filter—an LCD screen indicates when to change it—and a washable outer filter. A remote control (included) can be used to manually control the three-speed fan, and casters make the unit easy to move between and around jobsites. It’s listed on the company’s website for $600. Optional activated carbon and HEPA filters are available.