Dirt pockets are required on:

Dirt pockets, also known as dirt legs or sediment traps, are essential components in the installation of gas piping systems. They serve to collect moisture, dirt, and other debris that may exist in the gas supply line, thereby preventing these contaminants from entering and potentially damaging the appliance.

In the context of this question, dirt pockets are not required on decorative appliances, gas logs, or room heaters. These types of appliances are generally designed to operate without the need for dirt pockets because they typically operate at lower pressures and are less susceptible to the issues that dirt pockets aim to mitigate. Instead, dirt pockets are often a consideration for appliances that draw gas from the main supply line where contaminants might be present.

Therefore, the correct answer indicates that none of the listed appliances require dirt pockets, aligning with standard safety practices and appliance design considerations.