1.       There is no preceding latency but asthma symptoms commence during repeated intermittent or continuous inhalational exposures to non-massive, moderate, lower intensity but tolerable concentrations of an irritant vapor, gas, fumes or smoke.
2.       Asthma symptoms start during the time repeated irritant exposures take place and not after cessation of exposure.
3.       The duration of the repeated exposures is always more than 24 hours and typically does not last longer than 4 months of repeated exposures before asthma symptoms begin. Rarely does the irritant exposure last ³1-year before the initiation of asthma symptoms.
4.       There is the absence of pre-existing asthma symptomatology for the previous 1-year or there may be a past history of childhood asthma that resolved or there was a past history of adult asthma in remission for at least 1-year. There may have also been a diagnosis and/or treatment of bronchial asthma instituted by a previous physician.

5.       Typical irritant-induced asthma symptoms include episodic coughing, wheezing and symptoms of “bronchial irritability”, (i.e., acute respiratory complaints that follow exposures to various nonspecific irritants, physical factors and odors). There also may be intermittent chest tightness and nocturnal episodes of coughing, wheezing and breathlessness.
6.       Spirometry may be normal, show airflow limitation and/or demonstrate a positive response (³12%) to an inhaled bronchodilator.
7.       There is a positive methacholine challenge test (<8 mg/ml) that confirms the presence of nonspecific airway hyperresponsiveness.
8.       There must be exclusion of alternative conditions that simulate asthma including vocal cord dysfunction. The possibility of occupational asthma caused by a workplace sensitizer is also eliminated.
Table 2: Diagnostic Criteria for Repeated Exposure Irritant-Induced Asthma