A 37-year-old male non-smoker developed rapidly severe respiratory disease after a 3-hour exposure to hydrobromic acid fumes. An upper airway syndrome ensued with anosmia and aphonia as well as non-specific bronchial hyperreactivity, obstructive bronchiolitis (which led to a persistent respiratory volume of about 20% of the normal level with exercise-induced dyspnea) and obstructive bronchiolitis. Lung transplantation is currently being considered. When inhaled at irritant concentrations, certain toxic gases, such as chlorine, can lead to reflex apnea via laryngeal nerve reaction, limiting gas penetration into the bronchial tree. Other gases are cell toxins and can enter the deeper part of the lung before provoking irritating cough. This is what occurred for our patient who continued work in the polluted atmosphere until his severe cough obliged him to leave his job. This case is an example of cellular toxicity resulting from atmospheric gas fumes at low weakly-irritative concentrations, explaining the insidious nature of disease onset.