What is the necessary characteristic of ASD fan installation locations?

The correct characteristic regarding ASD (Active Soil Depressurization) fan installation locations is that it should not be placed in spaces where people occupy. This is critical because the ASD system is designed to mitigate radon gas, which can accumulate in indoor environments and pose health risks. By ensuring that the fan is installed away from occupied spaces, it minimizes the potential for radon exposure.

Additionally, placing the fan in unoccupied areas helps to manage noise levels and avoid any disturbances that could affect the comfort of occupants. The requirement to keep the fan out of occupied spaces is aligned with safety protocols and best practices for radon mitigation, ensuring that the system operates effectively while protecting individuals from potential exposure to radon and noise.

In contrast, visibility from a distance, being above ground level, and maintaining a constant temperature, while they might have roles in other systems, do not specifically address the critical needs in radon mitigation through ASD installations. The focus on avoiding installation in occupied areas reflects a dedicated effort to maintain indoor air quality while effectively managing radon levels.