Thanks for posting the query about your brother.
In my opinion, it is difficult to connect the smoking
and loss of awareness without ruling other possibilities. There are several reasons for 'passing out'.
I would suggest that he sees his family doctor in the first place and has some basic blood tests in addition to detailed assessment and examination. If deemed necessary by the doctor, he may benefit from an assessment by a neurologist
(to rule out neurological causes and some kinds of seizure
Hope that helps.
Dr Sandip Deshpande