Firefighters were called to a university campus in Leeds after reports of a possible chemical leak.
Crews attended University of Leeds' Civil Engineering building, in Woodhouse Lane, at around noon yesterday (Tuesday).
West Yorkshire Fire and Rescue Service said it had received reports of "a respiratory irritant" exposed to the building.
Specialist officers were on scene to ventilate the building and identify the source.
There were no reports of injuries.
Officers found no hazardous substances, and left the site at 3pm.