Pulmonary agents include chlorine, phosgene, diphosgene, oxides of nitrogen, chloropicrin, and perfluoroisobutylene (PFIB). They can be dispersed as a gas or aerosol and exert their effect by damaging the lung's alveolar-capillary membrane. This reduces oxygen exchange and allows leakage of fluid into the alveoli, producing pulmonary edema.

• Chlorine is an irritating, greenish-yellow, heavier-than-air gas with an acrid odor.
• Phosgene and diphosgene are heavier-than-air volatile liquids with the odor of fresh mown hay.
• Oxides of nitrogen are colorless liquids that produce an irritating vapor.
• Chloropicrin is a common agricultural biocide that is an irritating, clear-to-light green, oily liquid with an intense odor and the ability to produce lung damage at concentrations of only 20 ppm.
• PFIB is the combustion product of Teflon and other plastics and is 10 times more toxic than phosgene.

Following exposure to one of these agents, symptoms usually begin in minutes to hours, depending on the level of exposure. Exercise tends to accelerate the onset. Initial symptoms include eye pain and redness, lacrimation, sore throat, runny nose, coughing, and headache. After hours to several days, victims may develop nausea, hemoptysis, and the signs and symptoms of pulmonary edema, including choking, dyspnea, rales, hemoconcentration, hypotension, and possible cyanosis. Hypoxia and hypotension within 4 hours of exposure carry a poor prognosis.

Rarely, depending upon concentration of the gas and duration of exposure, pulmonary edema can occur within 30 minutes to 4 hours for chlorine and between 2 and 6 hours for phosgene. Most fatalities are within the first 24 hours and are due to respiratory failure.