This is what happens when there’s no ”AHJ” — Authority Having Jurisdiction.

Mayor Bloomberg says kids shouldn’t tour firetrap UN

The United Nations building is such a firetrap that Mayor Bloomberg is threatening to ban schoolchildren from touring the 55- year-old East Side landmark.

The city has given the UN until March to install smoke detectors and other crucial safety measures — or kids will be kept away.

Normally, the Fire Department can enforce code compliance. In this case, however, the New York Fire Department doesn’t have jurisdiction over the UN. Even though inspectors found 866 violations in January, no one can force the UN to bring the building up to code.