Vapour recovery device is an instrument to capture displaced vapours that emerge from inside a vehicle's fuel tank while filling petrol or diesel in it.
The CBCB issued notices to oil firms, seeking their explanation within 24 hours.
In separate notices issued to Bharat Petroleum Corporation Limited, Hindustan Petroleum Corporation Limited and Indian Oil Corporation Limited, CPCB Chairperson S P S Parihar said the pollution regulator's teams found that the vapour recovery systems were either not installed or not functioning at the fuel stations.
The teams have been deployed in the Delhi NCR to check the implementation of measures for combating pollution.
The CPCB sought the oil firms' replies within 24 hours "failing which, action as deemed necessary under the Environment Protection Act, shall be initiated".
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