Which system contributes to a building's fire suppression capabilities by controlling water flow?

The standpipe system is a crucial fire protection feature within a building, specifically designed to control and manage the flow of water for fire suppression purposes. These systems consist of a network of pipes and hoses that are strategically installed throughout a structure, allowing firefighters easy access to water in emergency situations. When a fire occurs, standpipes enable the prompt deployment of water directly to the fire area, effectively enhancing the building's fire suppression capabilities.

In contrast, heating, cooling, and ventilation systems primarily focus on climate control and air circulation within a building. While they contribute to overall safety and comfort in an occupied space, they do not directly impact the suppression of fires. Thus, the standpipe system stands out as the sole option that directly facilitates and contributes to controlling water flow during firefighting efforts, making it the correct answer in this context.