Several hundred staff and supporters of the Dublin Fire Brigade Ambulance Service have held a rally at City Hall in Dublin city centre.
They were protesting about fears that the ambulance service will be transferred from Dublin Fire Brigade to the HSE.
Trade union officials and politicians from all parties and groups warned that the service could be under threat from outsourcing and pledged to support it.
The rally also heard the accounts of two members of the public who relied on the service to save sick relatives.
The protesters are now heading to Liberty Hall for a meeting.
The HSE has confirmed that a review of the Dublin Ambulance Service has been commissioned and is ongoing.
The service is currently operated by Dublin City Council but funded by the HSE at a cost of around €10m a year.
IMPACT National Secretary Peter Nolan said the HSE proposals were unnecessary given what he called the excellent and efficient service already provided.
He noted that the Dublin Ambulance Service operates on around 7% of the national service budget, but responds to between 35% and 40% of ambulance calls nationally.
SIPTU Dublin Fire Brigade Convener Gerry Harris said members were extremely concerned about the proposals.