What must be approved regarding fireproof doors?

The requirement for approval regarding fireproof doors primarily focuses on the sealing of the door. This is crucial because the effectiveness of a fire door in preventing the spread of smoke and fire is significantly influenced by how well it is sealed. Proper sealing ensures that any gaps are minimized, thus enhancing the door's integrity during a fire event. Fireproof doors are designed to resist both flames and heat, but if the door is not properly sealed, it could allow smoke and heat to pass through, compromising safety measures in place to protect occupants and structure.

While the construction material, color, finish, and installation location of the door are important factors in fire safety and compliance, they do not directly impact the door's primary function of containing fire and smoke as intimately as the door’s sealing does. Therefore, the sealing of the door is essential to ensure that it performs effectively when required.