Typically a 'Negative Air Machine' refers to what are effectively Air Scrubbers (such as seen in the picture below). By attaching ducting to the machine, it is able to transport the unwanted air outside. Exhausting the air outside creates negative pressure inside the environment and helps inhibit the spread of polluted air to other areas inside the building.


An air scrubber can be used also to recirculate the air inside the property without exhausting outside. The configuration does not affect room pressurisation.