A ban on smoking in enclosed public places comes into force in the North today.
Support for the legislation is reportedly high, and the government is confident of a high level of compliance.
Environmental health officers and other officials will be out to ensure the ban is upheld.
Anyone who smokes in a no-smoking area will face a £50 fine; business premises face fines of up to £2,500 if they fail to enforce the ban.
The Ulster Cancer Foundation said the ban marked a new chapter in the health of the population. Gerry McElwee, head of cancer prevention at the charity, said: "We are absolutely confident that it will be an overwhelming success."
However, Mr McElwee said there was still a huge smoking health challenge facing Northern Ireland . "Every day eight local smokers die from diseases caused by tobacco; most are hooked before they reach the age of 16, and one in five babies are born to a mother who smoked through pregnancy."