The Act is similar to the English Health Act, but anticipates the English smoking ban by three months.
However, it means that company car drivers crossing into the Principality will need to comply with the regulations.
A Welsh Assembly Government spokesman said: ‘The legislation will apply to company cars used by more than one person when they cross the border into Wales from Monday onwards. Enforcement Officers in Wales will be providing advice and support to businesses about compliance.’
The new smoke-free rules classify cars and vans as a workplace if use is by more than one person. Such vehicles must display a ‘no smoking’ sign.
However, if only one person uses a vehicle, then smoking is permitted. Coupe-cabriolets are also exempt, but only while the roof is in the retracted position.
Smoking is permissible in privately run vehicles, but not where business use is in excess of 50% of the car’s annual mileage and where the vehicle may be shared by colleagues or clients. In such cases it, too, will need to be classified as smoke-free.
Pool cars and daily rental vehicles must also be smoke-free.