999 workers strike today
The operators at the facility in Navan are taking the 12-hour action in a long-standing row over pay and conditions.
Today's strike follows a previous stoppage in February. Patients requiring emergency services today will not be affected by the action.
Unions involved in the row say they want every member of staff to be given a living wage of €11.50, an increase of 50c per hour for some.
Ian McArdle of the Communications Workers Union says Conduit could have avoided the strike.