The central ventilation system KemJet for welding smoke extraction. It is a for workshops where local exhaust ventilation systems are not feasible or it is used to supplement such systems. It extracts contaminated warm air through exhaust pipes on the left and/or right of the filter unit. High-performance nozzles blow the purified, clean air out above the extraction pipes. The heated, purified air remains in the room, so that in the winter heat from the heating system is retained. This, way large energy cost savings can be achieved.