Abstract: Employee #1 was replacing a chlorine compressed gas cylinder for chlorinating water for a utility services company. The employee had to remove a chlorinator from the old chlorine cylinder and attach the chlorinator to a new cylinder. The chlorinator has a feed tube and a vent tube. The vent tube normally leads up through the roof of the shack and vents to the outside. Employee #1 removed the chlorinator, then inadvertently pulled down the vent tube from the roof. The vent tube tail end was lying on the floor just outside the entrance to the shack. When the employee energized the cylinder, he noticed the vent tube on the floor. He reached to pick it up, causing an increase in pressure within the tube and forcing the chlorine out. Employee #1 inhaled the vapors and became ill. He was hospitalized.