What is the industry standard for clearance around a steel door in a steel frame?

Where the doors are fire rated, these clearances are regulated by NFPA 80, “Fire Doors & Other Opening Protectives”. The clearance between the door and frame shall be a maximum of 1/8″. The clearance between the meeting edges of pair of doors shall be 3/16″. The clearance from the bottom of the door to the bottom of the frame should be a maximum of 3/4″. The clearance between the face of the door and the stop shall be 1/16″. See SDI 100 A250.8-2.1.8 for complete specifications.

While the clearances of non-fire rated openings are not regulated by the Building or Fire Code, they typically will follow the same values as a rated door.