Ozone, nitrogen dioxide, chlorine, and trichloramine are the principal oxidant gases to which man can be exposed in the work or general environment. Ozone is the main oxidant produced in the troposphere through UV-driven reactions involving nitrogen oxides and volatile organic compounds. Nitrogen dioxide is an indoor and outdoor pollutant generated by all combustion processes when at high temperatures oxygen combines with nitrogen. Chlorine is a corrosive gas mainly used in industry but is also released by some cleaning and disinfecting products. Trichloramine is a volatile by-product of water chlorination that contaminates the air of indoor swimming pools and various other indoor environments. All these oxidant gases are potential irritants to the eyes, the upper respiratory tract, and the lungs. Depending on the inhaled dose and the individual susceptibility, they can produce a wide spectrum of short-term effects including irritation symptoms, lung function impairment, airways inflammation, asthma exacerbation, and in extreme cases pulmonary edema and even death. The long-term effects of these gases are much less well documented although there is little doubt that repeated or chronic exposures to high levels of these oxidants are detrimental to the lung tissue and may lead to lung disorders, especially asthma or asthma-like syndromes (e.g., reactive airway dysfunction syndrome caused by chlorine). No specific antidote exists for these pulmonary irritants. Treatment is basically supportive according to the clinical manifestations.