Update: 1:40 p.m. A hazmat crew in the building got no hydrogen-sulfide readings; the gas has dissipated through the lab vent system.
Boston firefighters are at Boston College, at the Brighton/Newton line, where a liter bottle of hydrogen sulfide has leaked in Merkert Hall, inside a hood, at least, which might minimize exposure and its rotten-egg smell. Police have been requested to block traffic on Beacon Street.