Toxic pneumonitis is acute inflammation of the lungs induced by inhalation of metal fumes or toxic gases and vapors. It is a sentinel health event (occupational) associated with exposure to ammonia (refrigeration, fertilizer, and oil refining industries); chlorine (alkali and bleach industries); nitrogen oxides (silo fillers, arc welders, and nitric acid industry); sulfur dioxide (paper, refrigeration, and oil refining industries); cadmium (cadmium smelters and processors); trimellitic anhydride (plastics and organic chemical synthesis); and vanadium pentoxide (boilermakers). [Mullan] Chronic effects that have been reported after heavy exposure include bronchiectasis, bronchiolitis obliterans, and asthma. [LaDou, p. 366] The two types of pulmonary agents are central and peripheral. Central pulmonary agents, e.g., ammonia, are water soluble irritants that injure the upper airways. Peripheral pulmonary agents, e.g., phosgene, Nox, and PFIB, are slightly water soluble irritants that injure the alveolar-capillary membranes. Chlorine has both central and peripheral effects. Peripheral pulmonary agents cause pulmonary edema that is delayed up to 24 hours after exposure. The "4-hour rule" states that the victim has received a lethal dose if pulmonary edema develops within 4 hours. [USAMRICD, p. 19-35] Most of the agents of toxic pneumonitis can also cause chemical burns if vapor or liquid come in contact with the skin. Immediate decontamination with clothing removal and copious water irrigation should be considered for ammonia and other chemicals with significant skin and eye contact. [AHLS, p. 91-95; 480] "Pulmonary parenchymal injury that results from inhalation of irritant substances runs the spectrum of acute lung injury and includes pneumonitis, pulmonary edema, and the acute respiratory distress syndrome (ARDS). [Rosenstock, p. 334] In this database, agents linked to toxic pneumonitis are divided into two categories: primary and secondary. The primary chemicals can cause acute pneumonitis in animal experiments and are listed as toxic inhalation hazards (TIH) or releasers of TIH gases when spilled in water according to the 2012 Emergency Response Guidebook. These chemicals are linked to the occupational disease "Pneumonitis, toxic." The secondary chemicals are not linked to the occupational disease, but they are tagged with "Toxic Pneumonitis" as an adverse effect. Because of their importance in work-related exposures, cadmium fume, welding fumes, ozone, and elemental mercury vapor are also linked to the occupational disease even though they are not designated TIH. Also, all chemicals in the category "Corrosive Gases" are linked to the occupational disease.