Pub and club goers in south Wales will be breathalysed by door staff to see if they are too drunk to be allowed in.
Vale of Glamorgan council has received Welsh government funding for breathalysers for 12 venues.
The pilot scheme has begun ahead of the Christmas and new year period and follows similar trials across the UK.
Conrad Eydmann, from Cardiff and Vale health board, said it would show revellers that refusing them entry is an objective decision.
Substance misuse coordinator Benni Nicholson-Lepine added: “Recent health assessments show that… too many individuals are drinking at dangerous levels and we are aware of the increase in the number of individuals ‘preloading’ and being significantly intoxicated prior to going out for the evening.”