What makes Dyson vacuums unique is their common approach to capturing and storing dirt. First, Dyson vacuums have no bags or filters, so there is nothing to get clogged with dirt to reduce vacuum efficiency or make the motor run hot. Second, Dyson vacuums trap dirt in a clear plastic bin at the bottom of upright machines, expelling only clean air near the top. Other designs do a poor job of keeping dirt in the vacuum, claims Dyson.

Dyson vacuums operate much like huge industrial vacuums used to clean up debris from floods, hurricanes, and even the 9/11 collapse of the World Trade Center towers, and hazardous spills of radioactive materials. A miniature cyclone is created inside of a double-walled plastic tube by six plastic cones called “root cyclones”. Debris is sucked up the inner tube and spun by whirling air. Centrifugal force throws heavier dirt to the rim of the inner tube, where it spills over the rim and falls into the collection bin at the bottom of the outer tube. A plastic shroud about halfway up the inner tube traps lighter hair and dust, which also fall to the collection bin at the bottom.

Dyson vacuums come in upright, canister, and handheld models. Uprights range from the original DC07, which comes in "all floors" and "animal hair" subspecies, to the motorized, HEPA filter-equipped DC17, which Dyson claims outcleans all other brands. The newest member of the Dyson family is the DC18, a lightweight upright rated for all floors.

The company also sells a lavatory hand dryer called, ominously, The Air Blade. It is claimed to remove up to 99.9 per cent of bacteria from drying air, and to use 80 per cent less electricity than conventional hand dryers. More to the point, it dries hands 10 seconds faster than other brands. Its design is touch-free and it does not blow water and dirt onto bathroom floors.

Dyson vacuums are notoriously heavy; the DC17 weighs 20 pounds. According to Consumer Reports, which tests dozens of vacuums, Dyson vacuums "doesn't significantly outperform others" on bare floors, carpets, and pet hair-laden rugs. Dyson vacuums are fairly expensive, in the $450 to $600 range. But they now come with a 5-year warranty, apparently in response to past reviews that noted reliability problems. The entire Dyson vacuums line has been re-engineered in 2007, and seems to be more rugged than in the past. And they are easy to maintain, according to my housekeeper.

Godsend or gimmick, the Dyson vacuum is one of the world's most popular machines. If imitation is the sincerest form of flattery, then Dyson should be blushing with embarrassment. Many knockoffs are available at lower prices. But when buying any "cyclonic" vacuum, one should pay close attention to how well it keeps dirt inside, and to the general sturdiness and workmanship of the machine.