From BBC News :

New legislation which requires all homes in Scotland to have interlinked
smoke and carbon monoxide alarms will be delayed until 2022.

The moves followed criticism from Age Scotland and the Scottish
Conservatives over the lack of public awareness.

The new measures, which would cost an estimated £220 for an average
three-bedroom home, were due to come into force in February.

The Scottish government said MSPs would be asked to approve a 12-month
delay.

https://www.bbc.co.uk/news/uk-scotland-54621068
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Graeme