But China could arguably benefit more from them, considering its extreme air pollution.

So Chen decided to revamp his three-bedroom apartment near the Shanghai Railway Station when he moved in.

Workers followed his design to build four air outlets and intakes in the ceiling and furniture in the dining hall and three bedrooms. The main opening is in the southwestern bedroom.

The ducts are dotted with small holes and filters at their ends. Two motors over the bathroom expel air every two hours, using a timer in the shoe cabinet in the doorway.

Chen also installed PVC windows over the original windows, cutting down not only air pollution but also noise.

The materials cost 2,000 yuan. That's for 20 meters of PVC piping ranging from 10 to 15 cm in diameter, a timer, two silent motors and filter traps.

The rest went to paying laborers to install the system.

The facilities aren't visible. They're concealed in the interior design well enough that a visitor wouldn't know they were there unless told so.

Chen demonstrates the system by placing tissue on one of the intakes. It sticks.

"If someone smokes in here, the odor will disappear very quickly," Chen says.