Which of the following describes the impact of outdoor air entering an HVAC system when it is off?

When an HVAC system is off, the introduction of outdoor air can lead to energy waste due to the loss of conditioned air from the building. This occurs because the HVAC system is designed to maintain a specific temperature and humidity level inside. If outdoor air enters when the system is not active, it can displace the indoor air that has already been heated or cooled, leading to additional energy consumption once the system is turned back on.

Once the HVAC system resumes operation to counteract the temperature imbalance caused by the incoming outdoor air, it expends extra energy to bring the indoor environment back to the desired conditions. This unnecessary fluctuation in energy usage contributes to inefficiency and overall wasted energy resources. In contrast, the other options such as enhancing indoor comfort, leading to energy efficiency, or improving air quality would not accurately reflect the consequences of unregulated outdoor air entering a dormant HVAC system.