What should a technician check first when diagnosing airflow issues in a duct system?

When diagnosing airflow issues in a duct system, checking the air filter condition is essential because it is often the most immediate and easily accessible component that can impact airflow significantly. A dirty or clogged air filter restricts airflow, leading to inadequate system performance, increased energy consumption, and potential system damage due to overheating or other issues.

By ensuring the air filter is clean and in good condition, a technician can quickly determine if airflow is being affected by obstructions. If the air filter is found to be dirty, replacing or cleaning it can restore proper airflow, thereby alleviating the symptoms associated with airflow issues.

In contrast, while other factors such as refrigerant levels, isolation of air leaks, and compressor operation are important in overall system performance and efficiency, they would typically be assessed only after ruling out the simpler and more common issue of a compromised air filter.