What is a requirement for system monitors?

For system monitors, the requirement that they must be protected from the elements and clearly marked is critical to ensuring accurate measurements and maintaining equipment integrity over time. Protecting the system monitors from environmental factors like rain, snow, or extreme temperatures ensures that they function correctly and continuously provide reliable data about radon levels.

Moreover, having system monitors clearly marked helps in identification and promotes proper maintenance, ensuring that operators can quickly locate and check the monitors when necessary. This is particularly important in environments where multiple devices may be in use, preventing confusion and ensuring that safety protocols are followed.

While other options offer specific features that may be beneficial for system monitors, the requirement to protect them from the elements and have them clearly marked addresses both safety and functionality, making it an essential aspect of proper radon monitoring practices.