Airway irritation involves a variety of reflex mechanisms. Tracheal and bronchial C fibres and rapidly adapting fibres mediate cough, bronchoconstriction, and mucosal vasodilation. Workplace respiratory irritants can have a variety of effects in relation to asthma. Very high exposures can cause new-onset asthma, clinically presenting as reactive airways dysfunction syndrome or irritant-induced asthma. Symptoms after exposure to irritants depend on aggregate characteristics, water solubility and dose. Measurement of pulmonary function in response to irritants includes baseline spirometry, monitoring of across-shift changes and changes in non-specific bronchial responsiveness as well as bronchial responsiveness to inhaled allergens. Following irritant exposure, inflammatory changes within the airways are monitored by bronchoalveolar lavage or - less invasively - by sputum markers. A completely non-invasive approach not limited in repeatability is the investigation of inflammatory markers in exhaled air. However, the diagnostic and prognostic values of these novel markers have still to be demonstrated.