A cheap, no-electricity air conditioner that only requires recycled plastic bottles to work? It sounds too good to be true, but Bangladeshi innovator Ashis Paul has constructed a plastic bottle board, dubbed the Eco-Cooler, that can reduce indoor temperatures by 5° Celsius when installed in a window.

The idea was inspired by how humans blow air out of their mouths. Blowing air with an open mouth on the palm of your hand produces hot air. Reducing the area though which air passes can have a notable cooling effect: think about how your purse your lips to cool down hot soup or blow on a burn.

Creating an Eco-Cooler is simple: Several plastic bottles are cut in half and each bottle is attached to a piece of cardboard though creating holes as tight as the bottle’s rim. The board is then installed on an open window, with the cut bottle facing outward and the bottlenecks facing inward. Air passes through the cut plastic bottle and gets compressed at the bottlenecks, cooling as it enters the room.

In a country where 70% of the population lives in huts without electricity, this invention is a literal breath of fresh air. The invention, which has no copyrights and is encouraged to be replicated, has been adopted by global communications company Grey Dhaka and Grameen Intel Social Business, who install the Eco-Coolers in cities across Bangladesh including Nilphamari, Paturai, Daulatdia, Modonhati, and Khaleya.

“After initial tests, blueprints of the Eco-Cooler were put online for everyone to download for free,” the Managing Partner and Chief Creative Officer at Grey Dhaka said in an official statement. “Raw materials are easily available, therefore, making Eco-Coolers a cost-efficient and environmentally-friendly solution.”

This article was edited for clarity on 23 April, 2018.