Which of the following best describes Integrated Systems Testing (IST)?

Integrated Systems Testing (IST) is best characterized by simulating full building loads in testing conditions. This approach involves ensuring that all systems within a building—such as heating, ventilation, air conditioning (HVAC), electrical, and plumbing systems—work together effectively under real-world scenarios. By simulating these loads, testing can reveal how different systems interact when the building is operational, which is essential for optimizing performance, identifying potential issues, and ensuring that all components meet design specifications. This holistic testing methodology plays a critical role in the overall process of validating that a building's integrated systems will function as intended when occupied.

While the other options relate to various aspects of building systems, they do not capture the comprehensive nature of Integrated Systems Testing. For instance, simply starting up electrical devices or controlling mechanical systems does not encompass the broader goal of IST, which is to evaluate the combined performance of all integrated systems under realistic conditions. Similarly, error-detection methods in design focus more on identifying flaws in the planning stages rather than the functional assessment that IST provides after implementation.