Suncor Energy’s oil refinery is spewing 8.5 tons a year of invisible hydrogen cyanide gas over low-income north Denver neighborhoods, state records show. Community groups in Globeville, Swansea and Elyria this week petitioned the Environmental Protection Agency to require Colorado health officials to set a limit that protects people and at least require Suncor to disclose emissions of the gas to local emergency responders. CDPHE air quality control officials in January approved a change to Suncor’s air pollution permit that exempts the company from a federal requirement to disclose hydrogen cyanide emissions.