House alarm 9448 won't omit rooms?

Can anyone help me?

We have a 9448 alarm and it won't let me omit rooms when i set the alarm. I have found the manual online and it says to press the zone number followed by omit then enter the alarm code - but it doesn't work.

I am aware it won't let you omit a fire room? How do i find out if its a fire room I am trying to omit? Or how do i make it omit the zone?

Thanks!!