DENVER - Colorado gas and oil companies could soon face the strictest air quality rules in the U.S.

The state air quality board expects to meet four or five days starting Wednesday to adopt new rules, which have divided both the industry and the environmental community.

"These rules are incredibly important," said Dan Grossman, regional director for the Environmental Defense Fund, and a prime supporter of the plan.

The rules would require companies to detect leaks from their equipment and repair them quickly, and to stop venting methane into the atmosphere. It would be the first time any state in the country mandates the capture of methane.

Gov. John Hickenlooper announced his support for the proposal in November. He's backed by three oil and gas companies - Noble Energy, Anadarko and Encana - as well as the Environmental Defense Fund. But with most other energy companies opposed, and other environmental groups wanting a tougher rule, there's no guarantee the Air Quality Control Commission will give Hickenlooper what he wants.

Pollution from oil and gas equipment can pose a health hazard, because it can form ozone. Methane is a source of climate-changing greenhouse gases.

Hickenlooper's administration has estimated the rules would cut so much pollution of ozone-forming volatile organic compounds - more than 90,000 tons - that it would be like taking every car in the state off the road for a year.

The rules would apply statewide, but some energy companies and counties say they shouldn't apply to the Western Slope, which is in less danger of violating federal ozone standards.

Stan Dempsey, president of the Colorado Petroleum Association, said it doesn't surprise him that three energy companies are supporting Hickenlooper.

"They wrote the rules, secretly," Dempsey said.

Oil and gas companies were at the table for a year of negotiations. But in November, EDF and three companies broke off to create a plan, which Hickenlooper backs.

The Air Pollution Control Division estimates that complying with the rules would cost companies a combined $42 million a year. That's after a $17 million benefit from capturing natural gas that is currently vented to the atmosphere.

But Dempsey said his group's economist thinks the cost will be $100 million a year.