Which of the following should not be contained within a concrete floor?

In the context of construction and safety practices, unsleeved gas pipes should not be contained within a concrete floor due to the inherent risks associated with gas leaks. Concrete is a dense and impermeable material, which can trap any gas that may leak from the pipe, creating a hazardous environment. Should a leak occur, the gas would have limited ventilation, significantly increasing the risk of explosion or poisoning.

Gas lines typically require careful installation and may be subjected to various codes and regulations that dictate how they should be installed. These codes often specify that gas lines should remain accessible for maintenance and inspection, and unsleeved pipes do not provide the necessary protections or intervention points in the event of a failure.

In contrast, water lines, drain lines, and electric conduits are commonly encapsulated within concrete flooring when installed properly. These systems are typically designed to handle the conditions and stresses of being embedded in concrete and can be monitored and maintained without compromising safety.