Psychiatric nurses are taking action to highlight a lack of resources in Waterford and Kilkenny.
Action begins today at University Hospital Waterford and in residential units at Grangemore, St Aidens and Ard na Deise.
Members of the Psychiatric Nurses Association at the facilities voted 89% in favour of industrial action
The action will see psychiatric nurses refuse to co-operate with non-nursing duties.
Meanwhile, industrial action is 'escalating' at St Lukes Acute Psychiatric Unit in Kilkenny.
Action has been under way there since December, with the PNA suggesting overcrowding is continuing.
The PNA's Michael Hayes says members believe both patient care and staff safety is being compromised.
He observed: "Our members have decided to take this action, not just to safeguard their health & safety - but obviously that of their patients.
"The message to the HSE from today is clear – the current levels of overcrowding in psychiatric units in Waterford and Kilkenny cannot be allowed to continue.
"These vital services cannot be delivered adequately and safely in facilities that are regularly overcrowded and understaffed."
