Some IRC clients such as ircII, Epic, BitchX and so on may not come with a full european setting to be able to display characters such as å, ä, ö, ü, µ, € and so on properly. This is the way to fix this.
First set your language environment to avoid unicode:
export LANG en_US
Then start your IRC application and enter the following commands:
/set eight_bit_char on /set translation Latin_1
Now you should be able to use it properly.