A project to clean up emissions belched from Beijing's buses is being launched with help from the United States' Environmental Protection Agency (EPA).
A pilot project to modify 25 buses is expected to reduce their respirable particle emissions by up to 90 percent, said Merrylin Zaw-Mon, director of the Certification and Compliance Division of the US EPA.
Pei Chenghu, vice-director of Beijing Environmental Protection Bureau, believes respirable particles are a major threat to Beijing's air.
"At the moment, excessive respirable particles are the most serious pollutant in Beijing's air. Many of those particles are emitted by diesel engines," he said.
According to Zaw-Mon, a filter and diesel oxidation catalyst will be fitted to the vehicles, which will then be run on low sulphur diesel.
"If successful, we hope the modifications can spread to all Beijing's diesel engines," she said.
Currently about 120,000 diesel-fuelled vehicles are on the road in Beijing. Of these, only 24 percent conform to the Euro II exhaust emissions standard, while 37 percent do not even meet the Euro I standard, Pei said.
It is hoped the project can help Beijing experience more "blue sky days."
