The law in Scotland has changed and as of 1 February 2022 every home now needs to have interlinked fire alarms. So you should check your alarm if they complies with the standards - Carbon monoxide detectors: British Kitemark EN 50291-1
There are 2 types of interlinked fire alarms that meet the new rules:
sealed battery alarms – which should be tamper-proof long-life (which can be up to 10 years) batteries. You can fit these alarms yourself.
mains-wired alarms - these are cheaper than tamper proof long-life battery alarms, but should be installed by a qualified electrician. These should be replaced every 10 years.
Both types of alarm are interlinked by radio frequency without the need for WiFi.
If the carbon monoxide alarm is battery operated, it must have a sealed battery for the duration of its lifespan, which may be up to 10 years.