Dublin Fire Brigade is under-resourced and there is poor quality information about the risks involved when attending some calls, a union representative has said.
It comes after disturbances in the capital this week at a site that was due to be used to house International Protection applicants.
Speaking on RTÉ's Morning Ireland, SIPTU organiser Geoff McEvoy said the fire service responded to a blaze reported at the old Crown Paints factory in Coolock on Monday.
When members arrived, they could not quickly deal with the fire due to the situation at the site, with protesters at the scene.
The delay meant fire trucks were not available to the rest of the city, he added.
Because of the location, the initial suspicion was that this was an industrial fire, and the response was appropriate to what would be needed for an industrial fire, with three fire trucks, a high-rise ladder and the district officer dispatched.
However, he said when the firefighters arrived they were "caught in the midst of a confrontation between a group of individuals and An Garda Síochána".
"Just as we saw at the Dublin riots back in November, the particular nature of that situation, the heightened tension, the risk of violence, meant that the fire crews weren't able to extinguish that fire, which turned out to be just in a in a digger," Mr McEvoy said.
"But they weren't able to extinguish that fire as quickly as they would have been. So those resources then were tied up at that location for much longer than was necessary," he added.
The incident highlighted two issues that have "dogged the service for years", he said: under-resourcing in terms of staffing and poor quality information about the risks that are out there in the city.
"So, when I talk about the first and under-resourcing and short staffing, I mentioned that there were three fire trucks at that scene. But that day there were already four trucks that were what we call off the run.
"In other words, [they were] not available for service because of short staffing. So, with three trucks at the scene, four not available, that's seven in total that weren't available for the rest of the city for the duration, and that's the guts of half the fleet.
"That means that for the whole rest of the city, they're only covered by half of the fleet for the whole rest of that incident.
"Then that creates a risk to firefighters and to the public because it means that if there is another incident, which there was, trucks are going to have to respond from further afield and that creates delays and delays create additional risk, and we say any additional risk to the public or to firefighters is unacceptable."
SIPTU is in negotiations with the employer trying to agree a new overall staffing figure, he said.
"We reckon there's possibly about 100 more staff that are needed and to be fair there has been recruitment over the past two years and the problem is not getting better.
He said that there was years of non-recruitment which has created "a massive hole" within the service.
