500 ambulance personnel are striking today, in a dispute with the HSE over union recognition.
The crew members, who are part of the Psychiatric Nurses Association, will picket outside ambulance bases in Dublin, Cork, and other locations between 7am and 5pm.
The National Ambulance Service says it has detailed contingency plans in place.
That includes having Defence Forces paramedics on standby, managers carrying out frontline duties, and confirmation that personnel from other unions will be working as normal.
Peter Hughes, General Secretary of the PNA, says contingency plans are in place to deal with emergencies during today's strike action.
"From 7am to 5pm our members will be on strike," he said.
"We will cover emergencies, so emergency cover will be provided. Non-emergency will not be provided."
Ambulance personnel who belong to the PNA want the HSE to recognise the trade union as well as deduct and remit their subscription fee from their pay.
The HSE says it already recognises Siptu, Unite and Forsa, and thinks engaging with any further organisations would harm good industrial relations in the National Ambulance Service.
Siptu - which represents the most frontline staff - has confirmed that it expects its members to work as normal today.
The PNA says it will not call on other unions to join the strike and will provide emergency cover where necessary.