Created by an Indian-origin researcher, an inexpensive metal insert for primitive cooking stoves or what are commonly called "chulhas" may decrease use of firewood and reduce smoke, thereby potentially saving the lives of thousands of women and children.

When using firewood to cook on the poorly ventilated and inefficient chulhas, which do not have chimneys, smoke and soot settles inside the home and it also results in black carbon emissions which are known to cause respiratory diseases.

The World Health Organisation estimates that some 2.7 billion people worldwide still rely on food cooked by burning wood and more than four million people die prematurely each year from illness connected to household air pollution from that method of cooking.

H.S. Udaykumar, professor of mechanical and industrial engineering at the University of Iowa in the US, spent several weeks earlier this year in the western India region of Rajasthan investigating ways to reduce the amount of firewood used for daily cooking by women in the village.

After failed attempts at getting women in the village to use high-efficiency stoves made of metal -- partly because of their $30 cost -- researchers came up with the idea of a metal grate insert for the three-stone hearth stoves called chulhas, the women refused to abandon.

The insert, called Mewar Angithi, is made from a steel plate with air holes punched in it. The device costs about $1.

"It is a glorified grate, really. And so it is simple to make," Udaykumar, an alumnus of the Indian Institute of Technology, Madras, said.

The insert separates the ash from the wood and allows air flow from under the burning wood, which increases its efficiency.

Researchers found that using the metal insert reduced wood consumption by about 60 percent and anecdotally observed a significant reduction in smoke, although no formal emissions measurements were taken in the homes.

Further testing on soot emissions was later conducted in a national lab in India, and Udaykumar and his team found that the metal insert actually decreased emissions by 90 percent.

About 2,000 of the inserts are in use at present, and additional research will take place in India this winter, Udaykumar said.

The findings were reported in the journal Solutions.