The ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) Technical Committee 9.9 provides thermal guidelines for data processing environments. For typical enterprise-grade servers and equipment (classified as A1 and A2), the recommended environmental envelope for air entering the IT equipment is a dry-bulb temperature between 18°C and 27°C (64.4°F and 80.6°F). This range is established to balance optimal equipment reliability and performance with the goal of improving data center energy efficiency by reducing overcooling.

A. 8-18 °C (46.4 - 64.4 °F): This range is too cold; its upper limit is the minimum recommended temperature, leading to excessive and inefficient cooling energy consumption.

B. 20-40 °C (68 - 104 °F): The upper limit of 40°C falls into the allowable range for specific equipment classes (e.g., A3), not the universally recommended range.

D. 25-45 °C (77 - 113 °F): This range is too high and corresponds to the allowable limits for specialized, ruggedized equipment (e.g., A4), not the standard recommended guideline.

1. ASHRAE. (2021). Datacom Equipment Power Trends and Cooling Applications

Second Edition. ASHRAE TC 9.9. In Chapter 2

"Datacom Equipment Environmental Specifications

" Table 2.1

"Server Environmental Specifications

" the recommended dry-bulb temperature range for equipment Classes A1 through A4 is listed as 18°C to 27°C.

2. ASHRAE. (2015). Thermal Guidelines for Data Processing Environments

Fourth Edition. ASHRAE TC 9.9. In Chapter 2

"Environmental Guidelines

" Figure 2.1

"ASHRAE Environmental Guidelines for Datacom Equipment

" the psychrometric chart visually depicts the "Recommended" envelope with a dry-bulb temperature range of 18°C to 27°C.

3. Lawrence Berkeley National Laboratory. (2016). Best Practices Guide for Energy-Efficient Data Center Design. LBNL-1005892. In Section 3.1.1

"ASHRAE TC 9.9 Environmental Guidelines

" page 13

it states: "The recommended range for the IT equipment inlet air temperature is 18 to 27°C (64.4 to 80.6°F)."

A data center houses the critical IT infrastructure—servers, storage, and networking—that runs an organization's essential applications and services. Therefore, an unplanned outage of the data center directly translates to an outage of these business services, causing business downtime. This downtime leads to tangible negative impacts such as lost revenue, decreased productivity, damage to brand reputation, and potential regulatory penalties. The data center's availability is intrinsically linked to the business's ability to operate and generate revenue.

A: Data centers are integral to, not independent of, the business; they host the core IT systems required for operations.

B: Budgeting for contingencies is a risk mitigation strategy; it does not eliminate the actual business impact of downtime when it occurs.

D: Data center downtime affects virtually all modern industries reliant on IT, including finance, healthcare, and retail, not just airlines.

1. Patterson

D. A. (2014). The trouble with real-world data center availability. ACM Queue

12(10)

20-29. In Section "The Cost of Downtime

" the article explicitly links data center failures to the unavailability of large-scale internet services

which directly impacts business results. (DOI: https://doi.org/10.1145/2685691.2685695)

2. University of California

Berkeley. (Course: CS 162

Operating Systems and System Programming). Lecture notes on "Availability & Reliability

" Section 2: The Cost of Failure. These materials detail how infrastructure failures

such as those in a data center

translate directly to service outages and quantifiable business losses

including revenue and user trust.

3. Ko

R. K.

& Lee

B. S. (2011). A study on the economic impact of data center outages. IEEE Transactions on Reliability

60(1)

123-135. The entire paper is dedicated to modeling and quantifying the direct and indirect financial losses businesses suffer as a result of data center downtime. (DOI: https://doi.org/10.1109/TR.2010.2104019)

A service corridor is a critical architectural component in modern data center design, particularly for facilities aiming for high availability. It is a secure, restricted-access area that typically runs adjacent to or around the main computer room (white space). This corridor houses essential support equipment such as Computer Room Air Conditioning (CRAC) units, Computer Room Air Handler (CRAH) units, and power distribution panels. Its primary function is to allow technicians and engineers to perform routine maintenance, monitoring, and emergency servicing on this infrastructure without needing to enter the highly controlled and secured computer room environment. This separation minimizes the risk of operational disruption, human error, and contamination within the critical IT space.

A. This describes the function of a media storage room or vault, which is a separate, specialized area designed for long-term, environmentally controlled storage of backup media.

B. This definition is too generic. While a service corridor is a pathway, its specific purpose is for servicing equipment adjacent to the computer room, not just for general access.

C. This describes a generator room or enclosure. Generators require significant ventilation and are typically located in a separate, dedicated space, often outside the main data center building.

1. TIA-942-B: Telecommunications Infrastructure Standard for Data Centers. Annex G

"Data center space planning examples

" illustrates layouts where service corridors provide access to the rear of equipment racks or to mechanical and electrical equipment from outside the computer room. This design supports the principle of separating service activities from IT operations

as recommended in Section 5.3.3

"Architectural Design."

2. Uptime Institute

"Tier Standard: Topology

" (2018). The standard for Tier III certification requires "Concurrent Maintainability." A service corridor is a common design topology used to meet this requirement. It allows any single piece of capacity equipment (like a cooling unit) to be taken offline for planned maintenance without impacting the IT load

as access is provided from outside the computer room. (See Section 4.0

"Tier III: Concurrently Maintainable").

3. Turner

W. P.

& Seader

J. H. (2006). Data Center Design and Implementation. In Energy-Efficient and High-Performance Data Centers. This type of academic and professional text on data center design explains that service corridors are a best practice for isolating maintenance activities from the critical environment

thereby enhancing both security and operational uptime. The concept is foundational to creating concurrently maintainable facilities.

For life safety and emergency egress, doors from a computer room must swing in the direction of exit travel, which is outwards. This is a mandatory requirement stipulated by major safety standards such as the NFPA 101 Life Safety Code. In an emergency, personnel will push the door to exit; an outward swing facilitates a quick and unobstructed evacuation. Furthermore, an outward-swinging door helps to maintain the integrity of the room seal during the discharge of a gaseous fire suppression system, as the internal pressure pushes the door more firmly into its frame, preventing the suppression agent from escaping.

B. Instead of swinging doors, sliding doors are preferred: Sliding doors are generally not permitted for primary emergency egress paths as they can be difficult to operate in a panic and are more prone to jamming.

C. Depends on the type of Computer room: The requirement for doors to swing in the direction of egress is a fundamental life safety principle that applies universally, regardless of the computer room's specific type.

D. Inwards, code permitted: An inward-swinging door creates a dangerous obstruction during an emergency evacuation and would violate fundamental principles of life safety codes in virtually all jurisdictions.

1. Telecommunications Industry Association (TIA). ANSI/TIA-942-B. Telecommunications Infrastructure Standard for Data Centers. June 2017.

Section 6.2.4

"Doors

" explicitly states: "All doors for personnel access shall swing out of the computer room." This is a direct and unambiguous requirement from a primary data center design standard.

2. National Fire Protection Association (NFPA). NFPA 101®

Life Safety Code®

2018 Edition.

Section 7.2.1.4.2

"Door Swing

" mandates that doors swing in the direction of egress travel when serving high-hazard contents areas. Data centers

with their high concentration of electrical equipment

are typically classified as such

making outward swing a requirement for life safety.

3. National Fire Protection Association (NFPA). NFPA 75

Standard for the Fire Protection of Information Technology Equipment

2020 Edition.

Chapter 4

"Construction Requirements

" and Chapter 8

"Gaseous Agent Extinguishing Systems

" reference the need for room integrity and proper egress paths

which are supported by outward-swinging doors that comply with NFPA 101. The explanatory material in A.8.1.2 discusses the importance of tightly sealed rooms for gaseous agent effectiveness

a condition better maintained by outward-swinging doors under discharge pressure.

The notation "X/Y µm" for an optical fiber cable specifies the diameters of its two most critical components. The first number (50) represents the diameter of the central core, which is the path through which light signals travel. The second number (125) represents the diameter of the cladding, a layer of glass or plastic surrounding the core. The cladding has a lower refractive index than the core, causing total internal reflection that confines the light within the core. Both measurements are in micrometers (µm). This 50/125 µm specification is standard for OM2, OM3, OM4, and OM5 multi-mode fibers.

A: These numbers define the physical geometry of the fiber, not performance characteristics like data rate over a specific distance.

C: The 125 µm value is the diameter of the cladding only. The buffer and jacket layers are external to the cladding and increase the total cable diameter significantly.

D: This notation is unrelated to installation requirements, such as the necessary separation distance from electrical power cabling.

1. Mynbaev

D. K.

& Scheiner

L. L. (2001). Fiber-Optic Communications Technology. Prentice Hall. In Chapter 2

"Optical Fibers: Structures

Waveguiding

and Fabrication

" the text explains that fiber dimensions are specified by the core and cladding diameters

citing 50/125 µm as a common example for multi-mode fiber (pp. 45-47).

2. Cornell University

School of Electrical and Computer Engineering. (n.d.). ECE 4330: Fiber-Optic Communications

Lecture 2: Optical Fibers. Course materials describe the structure of optical fibers

stating

"A typical multimode fiber has a core diameter of 50 or 62.5 µm and a cladding diameter of 125 µm." (Section 2.1

"Step-Index Fiber").

3. The University of Texas at Austin

Department of Electrical and Computer Engineering. (n.d.). Introduction to Fiber Optics. Courseware notes state: "Multimode fiber is identified by the core and cladding diameters

expressed as core/cladding. For example

a 50/125 multimode fiber has a 50 micron core and a 125 micron cladding."