Ysbyty Gwynedd in Bangor will be holding a Major Incident training exercise today, Friday 13 September, between 9am-1pm.
The response involves a number of areas in the hospital which will allow staff to be ready should a major incident ever occur in North Wales.
The public are being informed as they are likely to see the exercise if they are visiting the hospital today or attending for an appointment and to not mistake it for a real incident.
The health board said that major incident training was “critical” for their staff to ensure they are fully prepared should a major incident ever take place in the area.
They added that there will be no impact on usual patient care or waiting times as a result of the training exercise.