Introduction Ozone-generating UV-lamps are used to remove unwanted grease from ventilation systems.

Irritant asthma after exposure to artificially produced ozone has been described at a Norwegian fish hatchery and a sewage plant, as well as in the Swedish paper industry.

We present cases that developed asthma after an accident with ozone-producing UV-systems in a restaurant kitchen.

Methods Case series Seven subjects that developed asthma were studied in relation to exposure, symptoms, medical history and clinical findings including lung function measurements, reversibility of airflow limitation and bronchial hyper responsiveness (BHR) to methacholine, both shortly after the accidental exposure and two years after the incident.

Result Out of a total number of 127 possibly ozone-exposed employees, 55 employees reported symptoms, and seven employees were diagnosed with occupational asthma after the incident. Six of these seven subjects had either positive reversibility and/or positive BHR tests.

Two years after cessation of exposure all seven subjects still needed treatment for asthma.

Three of the subjects had BHR despite the use of inhaled corticosteroids, all graded as ‘very mild BHR’. FVC, FEV1, FEV1/FVC ratio and FeNO values were within normal range in all cases. None had long absence from work or needed emergency treatment in hospital for their asthma.

Discussion The adverse impact of ozone exposure on the airways is well known from epidemiological studies, where the focus has been on the negative health effects of ozone (O₃) in ambient air, especially in large cities. Commercial use of the ozone gas’ odour absorbing and germ-killing properties has become more common in the last decade.

Accidents involving ozone gas from air purifiers with UV-lamps may cause acute irritant asthma. There is a need for greater awareness in the use of ozone-generating devices.