While vacuuming the floor at home one day, James Dyson noticed that his conventional machine (a Hoover, as it happened) was simply pushing dust around rather than collecting it. He decided to change its disposable paper bag, but when he found he had no replacements he sliced open the old one to empty it, planning to tape it shut again and reuse it. He discovered to his surprise that the old bag was not even half full, yet clearly it was affecting the suction power of the vacuum. Some days later he purchased new bags and set to experimenting. He soon realized that after even minimal usage, the pores of new paper bags became clogged with dust, thereby reducing the suction available to clean his floors. Clearly, there had to be a better way. Dyson already understood the basics of "cyclones," the inverted cones atop many sawmills that are used to capture airborne sawdust. He set about making a miniature version of a cyclone out of an empty breakfast-cereal box. He then jury-rigged his old Hoover with the cardboard cyclone and switched it on. He was amazed to discover that it worked, maintaining full cleaning power continuously, with no degradation of suction. After years of experimentation and thousands of prototypes he perfected the dual-cyclone technology that powers his products today: In a conventional vacuum cleaner, a motor and fan create suction, drawing air and dirt into a paper bag inside the machine and expelling "cleaned" air through a vent. In the Dyson vacuum, air and dirt are drawn into the top of a compartment containing an inner and outer cyclone. As the air and dirt make their first orbit around the outer cyclone they travel at about 20 mph. As the air continues to circulate around the gradually decreasing diameter of the inverted cone, however, it picks up speed. The high speed of the air increases the mass of the dust particles it carries by a huge factor. By the time dust reaches the bottom of the inner cone it is moving faster than 900 mph, or 324,000 rpm, and is "heavy" enough to fall to the bottom of the cyclone compartment. (Thanks to the laws of physics, Dyson's vacuums are able to pull dirt particles as fine as the elements of cigarette smoke out of carpets.) The air stream itself, now free of its load of heavy dirt, eventually passes through a purifying filter and is expelled back into the room through a "chimney" at the top of the dual-cyclone compartment.