Under what circumstance must an EEBD be removed from service?

An emergency escape breathing device (EEBD) must be removed from service if it has been tampered with because tampering can compromise the integrity and functionality of the device. The purpose of the EEBD is to ensure a safe means of escape in life-threatening situations where smoke or toxic gases may be present. If there is any indication that the device has been altered, modified, or interfered with in any way, the safety and reliability of the equipment are put at risk. Therefore, it is essential to remove it from service to conduct necessary inspections, repairs, or replacements to maintain safety standards.

In contrast, regular inspections (as mentioned in the choices), while important for maintenance, do not necessitate removal from service unless issues are found. Similarly, simply not using the device for a period of time or conducting a fire drill does not mandate removal, as long as the device remains functional and has not been compromised in any way.