At what height must a hall button be installed?

A hall button must be installed at a height of 42 inches according to the regulations. This standard height is established to ensure accessibility for all individuals, including those who may use wheelchairs or have other mobility challenges. By placing the button at this height, it is accommodating to a wide range of users, promoting ease of use and safety in access to elevators.

The choice of 42 inches aligns with guidelines laid out in building codes and accessibility regulations that emphasize universal access in public and commercial buildings. This height is considered a neutral position that is generally reachable by people of various heights, thus enhancing not only functional convenience but also compliance with accessibility standards.

The other height options provided either exceed or fall short of the recommended height, making them less suitable for installation if compliance with accessibility requirements is to be maintained. Therefore, 42 inches stands out as the correct and practical choice for the installation of a hall button.