First and foremost -- It is DOUBTFUL that you will need a Converter.  Most modern electronics come with dual voltage chargers.  Somewhere on the charging device should be a UL label.  If it states "Input voltage 1xx - 2xx VAC", or similar, all you need is a Plug adapter.  You only need a Converter to operate devices that are only rated for 110-120 VAC.

Ireland, and much of the rest of the world uses 220 VAC power, delivered at 50 Hz (Cycles per second), but the US and Canada operate on 120VAC, delivered at 60 Hz.  A converter changes the Voltage, but NOT the Hz cycling.  Most single-voltage appliances (like hair driers, curling irons, etc) would require a heavy-duty converter, rather than a light-duty, travel device  --  something rated for at LEAST 1500 Watts. 

Even then, using one will likely result in long-term damage to the device, as the different cycle rate is bothersome.

Most hotels and B&B offer / provide hair driers.  If you 'Need' such devices, either bring dual voltage units from home, or buy a cheap unit locally, after you arrive.

I bring a small, 3-outlet-from-1 adapter that I plug into my plug adapter.  This allows me to charge two (low load) devices -- say, my laptop and my cell phone or camera battery -- from a single outlet, since the total electrical load does NOT excede the rating for a standard outlet.

Bob

Those should work. Here is a photo of a plug and electrical outlet: http://www.p2p2007.org/pics/plug.gif See the little switch beside the outlet? http://edenvillasligo.webs.com/socket-jpg.jpg That turns the outlet on and off.