Question: A data center's HVAC system fails. Which immediate risk is most concerning?

A.  Fire

B.  Data theft

C.  Power outage

D.  Server overheating

Correct Answer:  D

Explanation:  

A. Fire
While fire is a significant threat in any data center, it is generally a secondary or tertiary risk in the event of an HVAC failure.

The Progression: For an HVAC failure to cause a fire, the ambient temperature would have to rise high enough to cause component combustion or electrical shorts.

The Safety Net: Modern data centers are equipped with independent fire suppression systems (like FM-200 or pre-action pipes) and thermal sensors that would likely trigger a controlled shutdown long before the "flashpoint" of hardware materials is reached.

B. Data Theft
HVAC (Heating, Ventilation, and Air Conditioning) is an Environmental Control, not a logical or physical access control.

Lack of Correlation: A failure in cooling does not weaken encryption, bypass firewalls, or unlock the physical cages where servers are kept.

The Exception: The only way data theft might increase is if the overheating forces technicians to open all security doors to create "airflow" (propping doors open), but as an immediate technical risk, data theft is unrelated to the cooling system.

C. Power Outage
HVAC systems and the power grid are separate infrastructures, though they are interdependent.

The Relationship: A power outage often causes an HVAC failure (if the HVAC is not on a generator), but an HVAC failure does not inherently cause the utility power to stop flowing to the building.

Indirect Impact: If the heat becomes so intense that it causes a catastrophic short circuit in a major power distribution unit (PDU), a local power failure could occur, but this is a consequence of the overheating, not the primary failure.

D. Server Overheating
This is the most immediate and certain risk when cooling is removed.

Thermal Density: Modern blade servers and high-density racks generate a massive amount of heat in a very small footprint. Without active cooling and airflow, "hot spots" can reach critical temperatures within minutes.

Hardware Protection: Most modern CPUs have built-in thermal protection (thermal throttling) that will slow down or shut down the server to prevent permanent physical damage. This leads to an immediate loss of Availability, as services go offline to save the hardware.

The CISSP Perspective: On the exam, always look for the "direct" result. HVAC = Cooling; therefore, HVAC failure = Heat.

Key Takeaway for the CISSP Exam

• Environmental Basics: Data centers must maintain specific temperature and humidity ranges.
• Too Hot: Equipment failure/overheating.
• Too Dry: Static electricity (ESD) risks.
• Too Humid: Corrosion and condensation.
• HVAC Goal: To maintain the "Sweet Spot" (typically 68°–77°F or 20°–25°C).