I worked for Prudential in Newark from 1985-1995. Though we were on the 4th floor of the Gateway building (the middle of the building), we kept smelling exhaust fumes. We complained to the people in charge of the facilities, but nothing changed. Finally we found out there was a heliport on the roof and they'd sit there idling- and there was an air intake port nearby.

They must have enacted rules about idling or changed the position of the helicopters, because the smell finally disappeared.