Bronchial challenge with direct stimuli, like histamine and methacholine, is very sensitive for diagnosing asthma and produces similar responses on a milligram-on-milligram or on a millimole-on-millimole basis [1–4]. American Thoracic Society (ATS)/European Respiratory Society (ERS) guidelines have proposed measures in order to protect technicians performing these tests, which include the use of good filters and ventilation, and have recommended that technicians with asthma should take extra precautions to minimise exposure or should avoid challenge testing. Performing methacholine/histamine challenge tests on technicians has also been thought to be useful [1]. Evidence however remains limited with only three published papers reporting some reaction to passive exposure in technicians [5–7], with two of these cited in the ATS/ERS guidelines [1]. One was a survey that only reported technicians' symptoms during challenge tests [5], another described two nurses who developed increased airway responsiveness after 2 years of regular practice of histamine and methacholine challenge tests, and the third paper reported episodic bronchospasm in a female technician known to have stable and well-treated asthma [7].