Alarm shielded cable, also known as fire alarm shielded cable, is specifically designed for use in fire alarm systems where electromagnetic interference (EMI) may be a concern. Here are some scenarios in which you should consider using alarm shielded cable in a fire alarm system:

1. High Electromagnetic Interference Environment: If your fire alarm system is installed in an environment where there are high levels of electromagnetic interference, such as near heavy machinery, electrical equipment, or radio frequency (RF) transmitters, alarm shielded cable can help mitigate the effects of EMI on the system’s operation.
2. Long Cable Runs: In installations where the fire alarm system requires long cable runs, there is a greater likelihood of electromagnetic interference affecting the signal integrity. Using shielded cable can help maintain signal integrity over longer distances and reduce the risk of signal degradation or false alarms.
3. Close Proximity to Power Lines: If the fire alarm wiring will be installed in close proximity to power lines or other sources of electrical noise, there is a higher risk of electromagnetic interference. Shielded cable can provide additional protection against EMI and minimize the risk of signal interference.
4. Critical or Sensitive Applications: In critical environments where the reliability and accuracy of the fire alarm system are paramount, such as hospitals, data centers, or industrial facilities, using shielded cable can help ensure reliable operation and minimize the risk of false alarms or signal disruptions.
5. Compliance with Regulations: Some building codes and regulations may require the use of shielded cable in certain fire alarm system installations, particularly in commercial or industrial buildings where electromagnetic interference may pose a safety risk or regulatory concern.
6. Enhanced Signal Integrity: Shielded cable can help maintain signal integrity and reduce the likelihood of signal distortion or attenuation, ensuring that alarm signals are transmitted accurately and reliably throughout the system.

The decision to use alarm shielded cable in a fire alarm system depends on factors such as the environment, the presence of electromagnetic interference sources, regulatory requirements, and the need for signal integrity and reliability. Consulting with a qualified fire alarm system designer or installer can help determine the appropriate cable type for your specific application.