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 that is caustic to the eyes, skin, nose, throat, and mucous membranes. Frostbite or chemical burns can occur in contact with the liquid. The Immediately Dangerous to Life or Health (IDLH) concentration is 10 ppm.

Phosgene (CG) and diphosgene are heavier-than-air, volatile liquids with the odor of freshly mown hay. The IDLH for phosgene and diphosgene is 2 ppm. Effects such as conjunctivitis, rhinitis, pharyngitis, bronchitis, lacrimation, blepharospasm, conjunctival hyperemia, and upper respiratory tract irritation may occur after exposure to concentrations of 3-5 ppm. Signs and symptoms of pulmonary toxicity include choking, chest tightness, severe dyspnea, pulmonary edema, cough, production of foaming and bloody sputum, nausea, and anxiety. Cardiac failure has occasionally occurred.

Nitrogen oxides are colorless liquids that produce an irritating vapor. Exposure typically results in cough, fatigue, and nausea but can also cause pulmonary edema, pneumonitis, bronchitis, bronchiolitis, emphysema, and possibly methemoglobinemia. The IDLH concentration depends upon the specific oxide but can range between 20-100 ppm.

Chloropicrin, also known as Chlor-O-pic, is a lacrimator and a lung irritant that is commonly used as an agricultural biocide. It is a clear to light green, oily liquid with an intense odor. Exposure may result in nausea, vomiting, dyspnea, headache, dizziness, cyanosis, pulmonary edema, and possibly death. Dermal contact can also result in dyspnea, headache, dizziness, and cyanosis. Ingestion can result in oral burns, sore throat, vomiting, and esophageal and stomach burns. In addition to lacrimation, ocular exposure may result in eye damage. The ILDH concentration for chloropicrin is 2 ppm.

PFIB, also known as octafluoroisobutylene, is the combustion product of Teflon and other plastics and is 10 times more toxic than phosgene. Exposure may result in sore throat, cough, nausea, headache, weakness, and dyspnea.

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. Signs and symptoms of pulmonary edema including choking, dyspnea, rales, hemoconcentration, hypotension, and possible cyanosis. Hypoxia and hypotension within 4 hours of exposure carries a poor prognosis. Rarely, depending upon concentration / time, 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 due to respiratory failure.