Which of the following is a mandatory requirement regarding gas appliance installation documentation?

Having the manufacturer's installation instructions available during the installation of gas appliances is a critical requirement. These instructions contain essential information specific to the appliance, including safe installation practices, operational guidelines, and maintenance procedures. Ensuring that these documents are on hand helps installers and inspectors verify that the installation complies with safety standards and codes. It serves as a reference to ensure the appliance is set up to operate correctly and efficiently, reducing the risk of hazards associated with improper installation.

Other options may be important in various contexts but are not as universally mandated for gas appliance documentation. For instance, while user manuals provide helpful operating information, they are not necessarily required to be present on-site during installation. Similarly, service history and building plans, while useful for maintenance records and structural considerations, respectively, do not have the same level of impact on the installation process as having the manufacturer's instructions readily available.