Help from California could be at hand to clean up the Calcutta air. To implement the Calcutta High Court order on Bharat Stage II compliance for vehicles plying in and around the city, Buddhadeb Bhattacharjee's government on Tuesday started negotiations with a California-based company on having a storage unit of compressed natural gas (CNG) set up at Haldia. According to the court order, all vehicles plying in the Calcutta Metropolitan Area (CMA) will have to conform to Bharat Stage II norms within April 2004, either by changing their old engines or by switching over to CNG or liquid petroleum gas (LPG).