Which item is prohibited from being installed in or attached to walls of combustible material?

Wall-type room heaters are prohibited from being installed in or attached to walls of combustible material due to the significant risk of fire hazards they pose. These heaters emit high levels of heat, which can easily ignite nearby combustible materials such as wood, drywall, or insulation, leading to potential fire incidents.

To ensure safety, wall-type heaters must be installed on non-combustible surfaces or in a manner that incorporates protective measures to create a safe distance from combustible materials. This restriction is vital for maintaining fire safety standards and protecting properties from the risks associated with high-temperature appliances.

In contrast, gas vents, pipe systems, and chimneys typically have established regulations that allow for their installation with the appropriate materials and clearance requirements designed to prevent fire hazards when properly installed.