Germany occupies Denmark during the Second World War, causing production at Nilfisk to fall dramatically. In the war years its attention turns to the industrial vacuum cleaner, which against all odds is launched in 1940. It subsequently proves to be a major success for the company.

Nilfisk utilises its manufacturing facilities as best it can manufacturing sidecars with stretchers for the Nimbus motorbikes used by the Civil Defence force. Oil rationing is the incentive for production of a gas generator for the Nimbus.

Both Nilfisk vacuum cleaners and Nimbus motorcycles are rationed to those with special needs for such products.

Tanned legs are produced using brown dye and a Nilfisk spray.