The machine they use is a modified Kleenrite. They have to put 5 litres of solution A and 5 litres of solution B into the machine. When these mix it creates carbon dioxide, hence the bubbles. It was all started by a guy who cleaned his carpet with a soda syphon. He got the stain out and he believed it was the bubbles which brought the stain to the surface. That idea is now a multi billion dollar worldwide business, unbelievable.