N10-009 Network Implementation Practice Question
A network administrator is installing cable in a plenum space (an area used for air circulation, such as above a drop ceiling). Which cable type is required by most building codes for such an installation?
⚠ Common exam trap
Test-takers frequently confuse 'plenum-rated' with 'riser-rated' or 'LSZH', assuming any low-smoke cable suffices, but the exam specifically tests that only CMP meets the fire and smoke spread requirements for plenum spaces as defined by the NEC.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Plenum-rated cable
Plenum-rated cable is required by most building codes (e.g., NFPA 70, National Electrical Code) for installation in plenum spaces because it is constructed with fire-retardant materials, such as FEP or PFA, that produce minimal smoke and are self-extinguishing. This prevents toxic fumes and flames from spreading through air-handling areas, ensuring safety in case of a fire. Standard PVC-jacketed cable would release hazardous smoke and support flame propagation, making it illegal in plenum spaces.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
PVC-jacketed cable
Why it's wrong here
Standard PVC (polyvinyl chloride) jacketed cables are highly flammable and pose severe hazards when exposed to fire, making them strictly prohibited in plenum spaces. Upon combustion, PVC releases dense, black, toxic smoke containing corrosive hydrogen chloride gas, which can obscure visibility, incapacitate occupants, and cause significant damage to electronic equipment. Their rapid flame spread and high smoke production directly contradict the safety requirements for air-handling environments.
When this WOULD be correct
PVC-jacketed cable would be correct for a question about general-purpose horizontal cabling in non-plenum areas (e.g., within walls or conduit) where cost is a primary concern and fire codes are less strict.
- ✗
Riser-rated cable
Why it's wrong here
Riser-rated cables are specifically engineered for vertical installations, such as running between floors in a building's vertical shafts or risers, and are designed to prevent fire from spreading upwards. While they possess some fire resistance, their flame spread and smoke generation properties are less stringent than those required for plenum spaces. Consequently, using riser-rated cable in a plenum space would violate fire codes and pose a significant risk, as it could rapidly propagate fire and dense smoke throughout the HVAC system.
When this WOULD be correct
A question asking which cable type is required for vertical cable runs between floors in a building (e.g., in elevator shafts or riser closets) would have riser-rated cable as the correct answer.
- ✓
Plenum-rated cable
Why this is correct
Plenum-rated cables are specifically engineered with advanced fire-retardant materials, such as fluorinated polymers like FEP or PVDF, which exhibit extremely low smoke production and flame spread characteristics when exposed to fire. This critical design ensures that in the event of a fire, the cable will not contribute significantly to the rapid distribution of smoke or flames through a building's air-handling systems. Adherence to stringent standards like NFPA 90A and UL 910 is mandatory for these cables to be installed in plenum spaces, protecting occupants and preventing widespread damage.
- ✗
Low Smoke Zero Halogen (LSZH) cable
Why it's wrong here
Low Smoke Zero Halogen (LSZH) cables are designed to emit minimal smoke and no toxic halogen gases when burned, making them suitable for confined spaces, particularly in European installations. However, despite their low-smoke properties, LSZH cables typically do not meet the rigorous flame spread and smoke density requirements specified by North American building codes (e.g., NFPA 90A, UL 910) for plenum spaces. Their primary benefit is reducing corrosive and toxic fumes, which is distinct from the plenum rating's focus on limiting fire propagation through air ducts.
When this WOULD be correct
In a scenario where the cable is installed in a non-plenum, confined space (e.g., inside a metal conduit or in a residential area) and the primary concern is reducing toxic gas emissions during a fire, LSZH cable would be the correct choice.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Plenum-rated cableCorrect answer▾
Why this is correct
Plenum-rated cables are specifically engineered with advanced fire-retardant materials, such as fluorinated polymers like FEP or PVDF, which exhibit extremely low smoke production and flame spread characteristics when exposed to fire. This critical design ensures that in the event of a fire, the cable will not contribute significantly to the rapid distribution of smoke or flames through a building's air-handling systems. Adherence to stringent standards like NFPA 90A and UL 910 is mandatory for these cables to be installed in plenum spaces, protecting occupants and preventing widespread damage.
✗PVC-jacketed cableWrong answer — click to see why▾
Why this is wrong here
PVC-jacketed cable is not allowed in plenum spaces because it produces toxic smoke and supports flame propagation, violating building codes that require low-smoke, fire-resistant materials.
★ When this WOULD be the correct answer
PVC-jacketed cable would be correct for a question about general-purpose horizontal cabling in non-plenum areas (e.g., within walls or conduit) where cost is a primary concern and fire codes are less strict.
Why candidates choose this
Candidates may assume PVC is standard for all indoor cabling and overlook the special fire and smoke requirements of plenum spaces.
✗Riser-rated cableWrong answer — click to see why▾
Why this is wrong here
Riser-rated cable is designed for vertical runs between floors, not for plenum spaces where air circulates. Building codes require plenum-rated cable in plenums due to its low smoke and flame spread properties.
★ When this WOULD be the correct answer
A question asking which cable type is required for vertical cable runs between floors in a building (e.g., in elevator shafts or riser closets) would have riser-rated cable as the correct answer.
Why candidates choose this
Candidates may confuse 'riser' with 'plenum' or assume that any fire-resistant cable is acceptable in plenums, not realizing that plenum spaces have stricter requirements.
✗Low Smoke Zero Halogen (LSZH) cableWrong answer — click to see why▾
Why this is wrong here
LSZH cable is designed to emit low smoke and no halogens when burned, but it is not specifically rated for plenum spaces; plenum-rated cable is required by building codes for air-handling spaces due to its fire-resistant and low-smoke properties.
★ When this WOULD be the correct answer
In a scenario where the cable is installed in a non-plenum, confined space (e.g., inside a metal conduit or in a residential area) and the primary concern is reducing toxic gas emissions during a fire, LSZH cable would be the correct choice.
Why candidates choose this
Candidates may confuse LSZH with plenum-rated cable because both are associated with fire safety and low smoke, but they are governed by different standards and applications.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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