Which of the following is NOT a benefit of maintaining proper HVAC system indices?

Maintaining proper HVAC system indices is crucial for ensuring optimal performance and efficiency of the system. Improved energy efficiency is a significant benefit, as an efficiently running HVAC system consumes less energy, leading to lower utility bills. Enhanced cleanliness of the air is another key benefit, as a well-maintained HVAC system can effectively filter and circulate clean air, contributing to better indoor air quality. Longevity of the HVAC system is also an important outcome; regular maintenance and proper operating conditions can prevent breakdowns and extend the life of the equipment.

Increased operating costs, however, do not align with the objectives of maintaining HVAC systems. Proper maintenance and operation are designed to reduce costs, not increase them. Therefore, this option indicates a negative aspect that is inconsistent with the benefits derived from maintaining HVAC system indices.