he integrated gas mixing system mixes the CO2 and O2 to your preferred level of mixtureMixing range for CO2: 2-10%, for O2: 2-20%The re-circulated, humdified and warmed gas combined with the Alu Heat system assures a stable temperature in the entire Work areaThe re-circulated gas has a Grade A quality achieved by circulation through a HEPA filter, a VOC filter, and a closed UV light chamberAir entering through the side ports during opening is absorbed by an upward suctionEasily changeable cuffs