Pissed on a barmans fart

exp.

Heard in Dublin and Louth

Describes someone with an extremely low tolerance for alcohol.

In use

Yer man cant handle his drink - he'd get pissed on a barmans fart.

Posh English

That fellow cannot hold his liquor at all. He would become inebriated by the merest whiff of a barman's flatulence.