Dirt pockets are required on:

Dirt pockets are specific to certain types of gas appliances to capture debris and contaminants that may affect performance. They play a role in ensuring better combustion efficiency and preventing blockages in the venting systems.

In this context, the answer indicates that none of the provided options are the correct applications for dirt pockets. Decorative appliances, gas logs, and room heaters typically do not require dirt pockets as a standard feature. These types of appliances often focus on aesthetics or are designed to be more self-contained in terms of combustion and exhaust systems. Hence, the absence of dirt pockets in these scenarios aligns with their operational requirements and maintenance protocols.

Understanding the specific requirements of gas-related appliances helps ensure safety and compliance with technical standards, which is critical for anyone working within this field.