Help, Please !

[DMOkada]

#1d) Noxious thing kept inside by Scot symbolically? (6,8)

Noxious thing = carbon monoxide but why ??

Thanks in advance for any explanation!

[scorpiojo]

CO (carbon monoxide) is in sCOt

[barry1010]

All I can see is CO (carbon monoxide) inside St.  Saints can be symbolic - if you see a saint with keys you know he's St Peter, for example.

Convoluted explanation, I'm sure somebody will parse it better

[scorpiojo]

...CO is the symbol

[barry1010]

Course it is.  

[bhg481]

This clue was so simple it's unbelievable but only scorpio was clever enough to spot it whilst the rest of us looked for something complicated. Well done scorpiojo!

[scorpiojo]

Thank you, bhg. 😊