Up to 500 ambulance workers nationally are planning to strike for a sixth day today.
The strike action will run from 7am until 5pm - as part of their campaign to be represented by the Psychiatric Nurses Association.
PNA ambulance branch members claim the HSE is attempting to force them to be members of unions they don't want to join.
They've warned they're prepared to escalate the strike, and have called an EGM for tomorrow week -18th April in Mullingar to consider further action.
Last week's strike saw PNA ambulance staff on the picket lines in Castlebar and Ballina.
However, staff had to leave the picket line outside the Sacred Heart Hospital in Castlebar to respond to emergency calls.