What is the approved method for closing abandoned inlet openings in chimneys and vents?

The correct answer emphasizes the necessity of following an "approved method" when it comes to closing abandoned inlet openings in chimneys and vents. This approach ensures that the closure is not only effective in sealing off the openings but also compliant with safety standards and building codes, which are designed to prevent hazards such as combustion gases leaking back into the building.

Using an approved method means employing materials and techniques that have been specifically validated for safety and performance in this context, ensuring that the integrity of the chimney or vent system is maintained and that the closure does not inadvertently create other issues, like trapping moisture or compromising structural integrity.

The other options, such as sealing tape, concrete blocks, or steel plates, might not be considered comprehensive or safe solutions by themselves. While they can serve as temporary fixes or might be used in certain scenarios, they may not fulfill the long-term requirements or safety standards established in the International Mechanical Code. Thus, relying on an "approved method" suggests adherence to best practices that have been tested and endorsed in the industry.