Reactive airways dysfunction syndrome (RADS) and irritant-induced asthma (IrIA) are closely related forms of asthma that result from the nonimmunologic provocation of prolonged bronchial hyperresponsiveness and airflow obstruction by inhaled irritants [1-3]. Irritant-induced respiratory problems were initially described among industrial workers and World War I combatants in the early part of the 20th century [4,5]. These reports focused on acute effects such as pulmonary edema and death, but also described chronic respiratory sequelae of intense, brief exposure to inhaled irritants .
Subsequently, bronchitic symptoms, such as cough and wheezing, were described following a chlorine spill in 1969, although bronchial responsiveness was not assessed . Persistent airway hyperresponsiveness was noted in five of seven subjects four years after an acute exposure to sulfur dioxide . Further studies have led to a growing awareness and understanding of reactive airways dysfunction syndrome and irritant-induced asthma, especially in firefighters, rescue personnel, and people living in the vicinity of the World Trade Center site in September 2001 [1,8,9].
The diagnosis and management of RADS and IrIA will be reviewed here. The diagnosis of asthma and the causes, evaluation and management of occupational asthma are discussed separately. (See "Diagnosis of asthma in adolescents and adults" and "Occupational asthma: Definitions, epidemiology, causes, and risk factors" and "Occupational asthma: Clinical features and diagnosis" and "Occupational asthma: Management, prognosis, and prevention".)
Reactive airways dysfunction syndrome (RADS) is described as the development of respiratory symptoms in the minutes or hours after a single accidental inhalation of a high concentration of irritant gas, aerosol, or smoke; these initial symptoms are followed by asthma-like symptoms and airway hyperresponsiveness that persist for a prolonged period (table 1) . RADS can occur after exposure to a variety of chemicals generated as gas or aerosol, or exposure to high levels of particulates (table 2). Clinical and functional criteria for the diagnosis of reactive airways dysfunction syndrome are listed in the table (table 1) .
Irritant-induced asthma (IrIA) is a more general term to describe an asthmatic syndrome that results from a single or multiple high dose exposures to irritant products . When only a single, high-dose exposure has been responsible, the term RADS is used. IrIA caused by single or multiple exposures to low doses of irritants has been reported, as after the World Trade Center catastrophe [8,9]. Multiple exposures to high concentrations of products, such as chlorine in pulp and paper mills, may be obvious enough for the affected person to identify the timing, nature, and frequency of events [10,11]. When IrIA is caused by workplace exposures, it is considered a type of occupational asthma, the non-immunologic type.