Abstract: An exhaust gas system for receiving and treating exhaust gases from different processing tanks including a hood supported by a moveable crane to direct exhaust gases from a selected tank to a selected exhaust duct. Exhaust gas then flows to a treatment site. A connector system is provided to connect the duct to the hood/crane combination. A flow rate sensor and air admission damper system is provided in association with the duct to sense the flow rate in the duct, to permit the addition of ambient air to the duct, by opening the damper, and thus assure a substantially constant flow rate to the treatment site.