The Irish Nurses and Midwives Organisation says their industrial action at St Vincent's Hospital in Dublin will continue until overcrowding is addressed.
Nurses at the Emergency Department are engaging in a work to rule, meaning only nursing duties are carried out.
INMO union members will refuse to do any tasks that do not involve direct contact with patients.
The union says patient safety will not be affected, and that emergency phone calls will be answered.
Director General of the HSE Tony O'Brien says hospital management have to engage with staff;
Nurses claim staff shortages are forcing them to carry out administration work, leaving less time to spend on medical duties.
They are also worried about overcrowding in the Emergency Departments and want emergency cases seen first.
Philip McAnenly from the Irish Nurses and Midwives Organisation says management have not even started talking about a solution:
Claire Best is a Nurse Manager in the Emergency Department in St Vincent's.
She says the current situation cannot continue:
