What is this on the roof

[crusher]

This picture from a E46 UK Spec bought by a friend. It is on the car roof interior. Any idea what is the function?View attachment 22544

 

[pratt]

I believe its a car ionizer.

 

[crusher]

THat's my first thought , but how does it work? Is there some control on the dash?

 

[lwloh]

it's the motion sensor for alarm.

 

[haywire]

Interior motion sensor as above comment.

 

[crusher]

Thanks for the info.