The Psychiatric Nurses' Association has begun national industrial action in protest at what it says is the understaffing of mental health services across the country.
Phase one of the industrial action involves non-co-operation with clerical and administrative duties, including the opening and closing of buildings.
The PNA National Executive Council will also meet next Monday to decide on the next phase of the industrial action.
It follows the failure of meetings involving the Health Service Executive, the Department of Health and a further meeting under the auspices of the Workplace Relations Commission yesterday.
Industrial action was sanctioned by 87% of PNA members in a recent national ballot.