The state Department of Health is restricting the use of electronic smoking devices known as "e-cigarettes" on its properties.

The ban will take effect Jan. 1.

Electronic smoking devices use a heating system to vaporized liquid nicotine, which smokers inhale.

State health officials Monday said the new policy applies to anyone who enters the department’s premises, including its employees, visitors, volunteers, students and contract and delivery workers.

Health official Lola Irvin said while electronic smoking devices are touted as smoke-free, they have not been proven to be safe.

Irvin, the department’s tobacco settlement programs manager, said e-cigarettes release nicotine and other chemicals and carcinogens into the air, possibly exposing people to harmful vapor, just like secondhand smoke.

The department said the new policy was among the last directives signed by its director, Loretta Fuddy, who died Dec. 11 after a plane in which she was a passenger crash-landed off Molokai.

The Food and Drug Administration is developing rules governing e-cigarettes.

The FDA said e-cigarettes have not been fully studied, and consumers have no way of knowing whether they are safe or how much nicotine and other potentially harmful chemicals are inhaled.

The federal agency has issued warning letters in the past to several e-cigarette distributors for what it says are unsubstantiated claims and poor manufacturing practices.

Cory Smith, owner of Volcano Fine Electronic Cigarettes, which operates a retail store on Oahu, said published studies have shown that secondhand vapor contains none of the toxins associated with combustible tobacco cigarettes.

"People who have made the switch to electronic cigarettes have made a conscious effort to remove themselves from that environment," said Smith, whose company manufactures and sells electronic cigarettes.