What type of fuel-burning appliances must be listed and labeled according to ASTM E 1509?

The correct answer is pellet appliances, as ASTM E 1509 specifically addresses the standards for testing and labeling pellet fuel-burning appliances. This standard ensures that these appliances meet safety, performance, and emissions criteria. By requiring that pellet appliances be listed and labeled according to this standard, it helps installers and consumers identify products that have been tested for reliability and efficiency.

Each type of fuel-burning appliance, including oil, gas, and wood, may have separate standards and testing requirements established by different ASTM or national standards, which is why they are not included under ASTM E 1509 in this instance. The specific focus on pellet appliances reflects the unique combustion characteristics and emissions of pellets, necessitating adherence to specific testing protocols to ensure safety and performance in their operation.