An additive manufacturing system , comprising: an unsealed air supply enclosure for clean air configured to be maintained at a first pressure above an ambient air pressure to inhibit unfiltered ambient air from leaking into the air supply enclosure; an unsealed processing chamber comprising a build mechanism configured to be maintained at a second pressure below the ambient air pressure to inhibit processing chamber air from leaking out of the processing chamber; an air pathway disposed between the air supply enclosure and the processing chamber to provide clean air from the air supply enclosure to the processing chamber; a first fan coupled to an inlet of the air supply enclosure to produce the first pressure in the air supply enclosure; a first filter coupled to an intake of the first fan to remove particulates generated in the processing chamber from the unfiltered ambient air drawn into the air supply enclosure by the first fan; a first pressure sensor disposed in the air supply enclosure to detect the first pressure; a first fan speed control to set an operating speed of the first fan; a second fan coupled to an outlet of the processing chamber to produce the second pressure and expel processing chamber air from the processing chamber; a second filter disposed between the outlet and the second fan to trap the particulates in the processing chamber air to inhibit the particulates from escaping the processing chamber. a second pressure sensor disposed in the processing chamber to detect the second pressure; a second fan speed control to set an operating speed of the second fan; and a controller coupled to the first pressure sensor and the first fan speed control and also coupled to the second pressure sensor and the second fan speed control to maintain the first pressure within a predetermined first pressure range higher than the ambient air pressure and to maintain the second pressure within a predetermined second pressure range lower than the ambient air pressure. an unsealed air supply enclosure for clean air configured to be maintained at a first pressure above an ambient air pressure to inhibit unfiltered ambient air from leaking into the air supply enclosure; an unsealed processing chamber comprising a build mechanism configured to be maintained at a second pressure below the ambient air pressure to inhibit processing chamber air from leaking out of the processing chamber; an air pathway disposed between the air supply enclosure and the processing chamber to provide clean air from the air supply enclosure to the processing chamber; a first fan coupled to an inlet of the air supply enclosure to produce the first pressure in the air supply enclosure; a first filter coupled to an intake of the first fan to remove particulates generated in the processing chamber from the unfiltered ambient air drawn into the air supply enclosure by the first fan; a first pressure sensor disposed in the air supply enclosure to detect the first pressure; a first fan speed control to set an operating speed of the first fan; a second fan coupled to an outlet of the processing chamber to produce the second pressure and expel processing chamber air from the processing chamber; a second filter disposed between the outlet and the second fan to trap the particulates in the processing chamber air to inhibit the particulates from escaping the processing chamber. a second pressure sensor disposed in the processing chamber to detect the second pressure; a second fan speed control to set an operating speed of the second fan; and a controller coupled to the first pressure sensor and the first fan speed control and also coupled to the second pressure sensor and the second fan speed control to maintain the first pressure within a predetermined first pressure range higher than the ambient air pressure and to maintain the second pressure within a predetermined second pressure range lower than the ambient air pressure. <EOS>