| 1. There is no preceding latency but asthma symptoms commence during repeated intermittent or continuous inhalational exposures to non-massive, moderate, low intensity but tolerable concentrations of an irritant vapor, gas, fumes or smoke. |
| 2. 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 ≥ 1-year before the initiation of asthma symptoms. |
| 3. 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. Atopy is frequent. |
| 4. Typical irritant-induced asthma symptoms include episodic coughing, wheezing and symptoms of “bronchial irritability,” (i.e., acute respiratory complaints that follow occupational and/or environmental exposures to various nonspecific irritants, physical factors, and odors). There also may be intermittent chest tightness and nocturnal episodes of coughing, wheezing, and breathlessness. |
| 5. Spirometry may be normal, show airflow limitation and/or demonstrate a positive response to an inhaled bronchodilator. |
| 6. There is a positive methacholine challenge test that confirms the presence of nonspecific airway hyperresponsiveness. |
| 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 |
