What provision is necessary for Type 2 clothes dryers with respect to make-up air?

For Type 2 clothes dryers, which are typically categorized as non-vented or combination appliances, the requirement for make-up air is critical for proper ventilation and safe operation. The provision that specifies a minimum area of 1 square inch per 1000 Btu/hr input ensures that there is adequate make-up air to replace the air that is exhausted during the drying process.

Adequate make-up air is important to prevent negative pressure in the environment where the dryer is used, which can lead to issues such as backdrafts from other appliances, accumulation of harmful gases, or inadequate dryer performance. By establishing this minimum area requirement, the regulation provides a baseline to ensure that there is enough fresh air available for combustion and functioning of the dryer, thereby promoting safety and efficiency in operation.

In contexts where options regarding maximum area or the absence of a requirement were presented, they would not suffice to ensure the necessary airflow for safe functioning. The minimum area requirement acts as a safeguard for both the appliance's efficiency and the safety of the users and the environment.