Zafira 2.2 1999 - can you use a key to turn off alarm under bonnet?

Alarm on my Zafira keeps going off, Catch 22 as cannot work on it to find out what problem is.. I got a small 2masterkey" when i bought car second hand and it appears this may be used to switch alarm off under bonnet. Does this sound true and if so where under the bonnet??