500 ambulance personnel are picketing at locations across the country today in a dispute over union recognition.
It is the second day of strike action by workers belonging to the Psychiatric Nurses Association (PNA).
They want the HSE to recognise the union of their choice, which is the PNA.
Two further strike days planned for February 28 and March 1.
Today's stoppage will take place for ten hours from 7am to 5pm.
The HSE has previously stated that they already recognise a number of unions including SIPTU, and it believes recognising further organisations will not be good for good industrial relations.
The National Ambulance Service (NAS), of which the staff are members, has made preparations for today’s strike so the service and care delivery is not compromised in any way.