The atmosphere of a fire is deadly to breathe. Firefighters or building occupants may be victims of the heat, irritating smoke, depleted oxygen, carbon monoxide, and such other toxic gases as cyanide, hydrogen chloride, and acrolein. Increasing numbers of homes and public buildings are being built and furnished with highly flammable synthetic materials that give off copious smoke and toxic gases when burned. Whether or not there are cutaneous burns, the possibility of inhalation injury must be considered in any fire victim. All victims of a fire environment should be presumed to have CO intoxication and should be treated with 100% oxygen until the HbCO level is within normal limits. In an extreme situation, cyanide intoxication should be suspected and administration of sodium thiosulfate may be lifesaving. Upper airway occlusion may result from thermal damage or edema secondary to burns from soluble toxic gases. Chemical injury to the lower airway and alveoli may result from inhalation of insoluble irritant gases and toxic gases adsorbed on carbon particles. Upper respiratory tract obstruction may be suggested by the clinical presentation (eg, pharyngeal burns, stridor, hoarseness, dysphagia), but only by means of fiberoptic bronchoscopy can it be recognized or excluded with certainty. Intubation may be necessary. Lower respiratory tract injury may be manifest clinically by dyspneas, wheezing and chest tightness, as well as by hypoxemia and reduced FEV1 and FVC. Treatment is symptomatic, but close observation for progressive respiratory insufficiency is necessary.