Type of wire to use for DSC PC1832

Hello, I am installing my new alarm system but I run short in wire, which is a 4-22. The DSC system requires to use wire with 18 to 22 Gauge. I have a bunch of speaker wire with 18 Gauge and I am wondering is it's safe to use for my last device I need to connect to the system. the device is a smoke detector. Any previous experience on this ? Thanks.