Which of the following is NOT a type of fire door?

The correct answer highlights that a countertop fire door is not recognized as a standard type of fire door within fire protection codes and standards. Fire doors are specifically designed and tested to prevent the spread of fire and smoke between different compartments in a building, and they come in several defined categories based on their functions and construction.

Self-closing fire doors are designed to close automatically to help contain a fire when activated, while fire-resistive fire doors are constructed from materials that have been tested for their ability to withstand fire for a specified period. Bi-folding fire doors can be used in certain applications where space efficiency is required and still meet fire protection requirements when installed properly.

Countertop fire doors do not exist as a recognized category in fire safety standards, making this option an outlier compared to the others that serve to enhance life safety and property protection in specific scenarios.