A Dublin Fire Brigade appliance was taken out of operation last night because of a staff shortage.
Siptu says there should be 169 firefighters and paramedics on at any one time to meet agreed safety standards.
However, only 138 were available to work last night, meaning one unit at Donnybrook Fire Station was out of action.
"Fire safety cover in the city was potentially down by 20%," said Siptu's Brendan O’Brien.
"Senior Officers mitigated some of this risk by trying to get people to report for overtime at the start of the shift but were unable to compensate adequately for the staff shortage, resulting in a fire appliance having to be taken out of service in Donnybrook.
"The lack of personnel trained to drive emergency vehicles is further exasperating the situation. This problem was foreseen and could have been averted by training more staff. If the situation is not addressed very quickly the depletion of fire cover is likely to get much worse."
Siptu has called for immediate action to increase firefighter/paramedic numbers in the Dublin Fire Brigade.
"As was highlighted on RTE’s Liveline programme yesterday, which included the case of an 87-year-old woman in Drumcondra who was informed that no ambulance was available to respond to her call, ambulance cover in the city is also at a critical point," said DFB Convenor, Shane McGill.
"During 2017, DFB ambulances responded to 114,613 calls. Call volumes are up year upon year, yet DFB is still operating with 12 ambulances despite a capacity review identifying the need for at least an additional four. All DFB ambulances are operated by dual trained crews meaning they are in operation 24-hours, seven days a week.
"The level of DFB recruitment planned for this year will not come close to addressing the current staffing crisis. It is essential that a decision is made to adequately resource the DFB Fire and Ambulance service. There must also be a fully independent review of the Fire-based Emergency Medical Service which is provided by the DFB in Dublin prior to any attempt to break it up."
- Digital Desk