Chlorine

... Irritating to nose & throat at 5 ppm or above ...

... Highly irritating especially to the mucous membranes of the eyes and respiratory tract.

Caution: Potential symptoms of overexposure are burning of eyes, nose and mouth; lacrimation, rhinorrhea; coughing, choking and substernal pain; nausea, vomiting; headache, dizziness; syncope; pulmonary edema; pneumonia; hypoxemia; dermatitis; direct contact with liquid may cause frostbite.