The group’s board of directors voted 15-1 on unprecedented new rules that will impose fees on factories, power plants, oil refineries and other businesses that emit carbon dioxide and other heat-trapping gases.

The agency, which regulates air pollution in the nine-county Bay Area, will be the first in the country to charge companies fees based on their greenhouse gas emissions, experts say. The new rules will take effect July 1.

The modest fee — 4.4 cents per ton of carbon dioxide — probably won’t be enough to force companies to reduce their emissions, but backers say it sets an important precedent in combating climate change and could serve as a model for regional air districts nationwide.