Under a sky darkened by thick black smoke, hundreds of thousands of brick kiln workers endure back-breaking labor and suffocating heat - working in almost medieval conditions across South Asia.
But a 7.8-magnitude earthquake that hit Nepal in 2015 killed about 9,000 people and flattened about a third of the country's brick kilns.
Despite the scale of the human tragedy, the devastation provided a rare opportunity for environmentalists to clean up at least one part of the notoriously filthy industry.
The Brick Kiln Initiative, launched by the International Centre for Integrated Mountain Development (ICIMOD), found a way to redesign the ovens and stack the bricks differently so that less of the toxic soot is produced.
“We have changed three things," explained Bidya Banmali Pradhan, program coordinator for the initiative. "One is more resistance to earthquake. The second is less polluting, and the third is energy efficiency.”
By stacking the bricks inside the kilns in a zig-zag pattern, the heat snakes through the gaps more efficiently, ensuring coal is completely burned, which produces less soot.
“I adopted this to clean up the environment," kiln owner Raj Kumar Lakhemaru said. "Business has its place but my primary objective was to produce high quality products efficiently and with less fuel. I think this is now being adopted by others across the country.”
Emissions were cut by 60 percent. And more importantly for the kiln owners, it reduced coal consumption by half.
“Since we adopted this zig-zag method... there is less pollution, we [are] using less coal and getting better bricks, faster," said Mahendra Chitrakar, president of the Federation of Nepal Brick Industries.
Most of the 100 brick kilns in the Kathmandu valley have already been modified with new technology. The next step is to spread the technology.
“In the coming two-three years, we intend to transform all brick kilns in Nepal. Let’s see," Mahendra said.
Brick manufacturers from Bangladesh, India, Nepal and Pakistan met in Kathmandu this year to discuss the new design.