From 6am today the smoking ban came into effect in Wales, which means that it is now illegal to smoke in any pub, restaurant, office or mode of public transport.
Anyone caught breaching the ban will be fined £50, but pub landlords and managers face much heftier charges.
Those who do not display adequate no-smoking signs will be fined £200 and landlords will face a fine of up to £2,500 if they allow people to smoke on their premises.
Moreover, many pubs have incurred extra expenses in an effort to provide adequate outdoor smoking facilities and signs.
Landlord Martyn Mears told icWales: "We're having awnings put up outside at great expense, as well as extra lighting and ashtrays.
"I think it's going to be very difficult, and it will really harm trade, which is going down anyway."
Philip Lay, retail director at SA Brain, Wales's biggest independent brewer and pub operator, said: "The only certainty is that business is going to go backwards for a while."
The smoking ban comes into effect in England on July 1st.
