The fire in the story is generally taken to represent Irish nationalism, the urge for independence from England. The story is overtly political, based as it is on the canvass for an election, and the various characters express diverse views on the political situation generally as well as on particular political and historical figures. All the while the fire is kept going, actually just about kept going, struggling to stay alight almost. Old Jack the caretaker (maybe even that's significant) is the one who pays most attention to it, while others barely notice it. The priest, for example, is in and out of the room in a flash, and doesn't go near the fire.
It is always difficult to know how seriously to take such symbolism in Joyce. The fire is such an obvious symbol of nationalism that he could be having fun with it, inviting extravagant conjecture and speculation from interpreters and critics. Bearing this in mind, how far do we go with cigarettes being lit from the fire and especially with the fire being used to open the bottles of stout that eventually appear? Irish nationalism is at its most fervent when alcohol comes into the equation, so it is very tempting to view the story as a satire on Irish politics. After all, most of these characters are sitting around talking rather than doing anything, and their talk contains a fair bit of gossip and backstabbing, so typical of Irish political discourse. They wear the Parnell 'badge', the ivy, but seem as concerned about the stout arriving as anything else. At the same time, some characters are active, sincere and committed, so it's not that simple. Look at each character carefully before making a judgement. Maybe sitting around the fire means token attention to the nationalist cause and staying away from it indicates actually doing something about it. As you are no doubt aware, Joyce can be a slippery fish at the best of times!
There is one point about the fire that I would welcome your view on. At one stage a couple of candles are lit from it and as a result the fire loses its cheerfulness (I haven't got the text to hand but it goes something like that). If the fire is symbolic, how do we interpret that?