This is the VOA Special English Development Report, fromhttp://voaspecialenglish.com

More than three billion people are at risk from indoor air pollution because of the heating or cooking fuels they use. Most live in Africa, India and China. They use biomass fuels like wood, crop waste, animal waste or coal. These solid fuels may be the least costly fuels available. But they are also a major cause of health problems and death.

For more than thirty years, the Aprovecho Research Center has been designing cleaner, low-cost cooking stoves for the developing world. Dean Still is the director of the group which is based in the United States. He notes a World Health Organization estimate that more than one and a half million people a year die from breathing smoke from solid fuels.

Mister Still says: "And half of the people on planet Earth every day use wood or biomass for cooking. These are the people on Earth who have less money, and the richer people use oil and gas. It's been estimated that wood is running out more quickly than oil and gas. And so it is very important for the poorer people to have very efficient stoves that protect their forests and that protect their health."

Every year Aprovecho holds a "stove camp" at its testing station in Cottage Grove, Oregon. Engineers, inventors, students and others come together to design and test different methods and materials for improving stoves.

Over the years, the group has made stoves using mud, bricks, sheet metal, clay, ceramics and old oil drums. Most of the stoves look like large, deep cooking pots. They have an opening at the bottom for the fire and a place on top to put a pot.

Through the years, Dean Still says his group has experimented with countless stove designs.

He says the goal is to make a very inexpensive stove that costs about five dollars. It would make very little smoke. So it would be safe for health, and reduce global warming and deforestation.

Aprovecho has now partnered with a stove manufacturer in China.

The company is making Aprovecho's first mass produced stoves.

They are said to use forty to fifty percent less wood than an open fire, and produce fifty to seventy-five percent less smoke. A company called StoveTec is selling them through its Web site for less than ten dollars. Dean Still says that more than one hundred thousand have been sold so far.

And that's the VOA Special English Development Report.