Regarding riser and plenum cables, which statement is true regarding replacement?

Regarding riser and plenum cables, which statement is true regarding replacement?

• A. Riser Can Replace Plenum But Not Vice Versa.
• B. Plenum Can Replace Riser But Not Vice Versa.
• C. They Are Interchangeable.
• D. Neither Can Replace The Other.

Answer: (B)

The key idea here is matching cable fire-safety ratings to the space they run in. Plenum-rated cables (CMP) are designed for air-handling spaces and have stricter flame and smoke requirements than riser-rated cables (CMR). Because of that, a plenum-rated cable can meet or exceed the needs of a riser space, so it can be used in a riser run as a replacement. But a riser-rated cable does not meet the stricter requirements of a plenum space, so it cannot be used in a plenum. In short: you can substitute plenum for riser, but not riser for plenum.

The key idea here is matching cable fire-safety ratings to the space they run in. Plenum-rated cables (CMP) are designed for air-handling spaces and have stricter flame and smoke requirements than riser-rated cables (CMR). Because of that, a plenum-rated cable can meet or exceed the needs of a riser space, so it can be used in a riser run as a replacement. But a riser-rated cable does not meet the stricter requirements of a plenum space, so it cannot be used in a plenum. In short: you can substitute plenum for riser, but not riser for plenum.