SALT LAKE CITY (AP) -- After a winter with back-to back episodes of severe pollution in northern Utah, Gov. Gary Herbert is once again urging all Utah residents to do their part to reduce pollution.

Officials have issued alerts on more than 20 days this year when atmospheric inversions have trapped cold air and pollutants in northern Utah's bowl-shaped mountain valleys, at times giving the area the nation's worst air.

Protesters fed up with Utah's dirty air have staged several rallies at the Capitol during this session and delivered petitions to the governor, criticizing him for not taking enough action to combat smog.

On Monday, the governor said there will always be criticism of his office and state lawmakers, but he said the government is taking steps to tackle pollution.

Herbert held a news conference Monday afternoon inside a school bus that runs on alternative fuel and said he's encouraging governments and businesses to shift to using vehicles that run on cleaner-burning fuels.

Herbert also announced his support for legislation introduced by Sen. Stuart Adams, R-Layton, which asks utility regulators to explore ways to convert more fleets of government vehicles to natural gas and set up natural gas fueling stations across Utah.

The bill allows a government agency to fund the conversion of government fleets and construction of fueling stations with bond money.

It will help get Utah "through this transition from what we feel is a fossil-fuel age into the new era of alternate fuels," Adams said.

The legislation is designed to encourage large groups of vehicles, such as school buses, to shift to natural gas, the governor's office said in a statement.

Hebert also highlighted other air quality legislation he supports.

One bill, from Rep. Jack Draxler, R-North Logan, extends a tax credit set to expire this year for people for buying an alternative-fuel car or converting a car to clean fuels.

Another proposal Herbert supports comes from Rep. Patricia Arent, D-Salt Lake City, which requires government agencies and school districts to develop and submit plans to curb emissions.

The proposal is part of a package of bills Democrats have introduced to combat pollution, including measures to expand access to public transit.

Herbert said the clean fuel legislation he touted Monday will not solve the pollution problem but is a "step in the right direction."

He also reiterated a call for all Utah residents to look for ways they can reduce emissions.

"We all contribute to the pollution that's out there," Hebert said Monday. "Therefore we should all contribute to the solution."