Understanding NFPA 101 for mission critical facilities

NFPA 101: Life Safety Code 2015 is a reference used for strategies to protect people based on building construction, protection, and occupancy features that minimize the effects of fire and other related hazards. It is the only document that covers life safety for new and existing structures. It is vital to understand the electrical/power systems in mission critical facilities and best practices.


This article is peer-reviewed.Learning objectives

  • Understand the occupancy-type classification for data centers.
  • Realize the differences in NFPA 101: Life Safety Code requirements for business and industrial occupancies.
  • Explain critical life safety system requirements.

What does a data center and a laundromat have in common? As far as the International Building Code (IBC) is concerned, they are both considered "Group B Business Occupancies." As per IBC Section 304 Business Group B, both types of businesses have the same basic set of minimum requirements to safeguard the general health and welfare of occupants. Group B Business Occupancies are generically defined as occupancies that include office, professional, or service-type transactions including storage of records and accounts. Data centers and laundromats fall under the listed subset business uses of "electronic data processing" and "dry-cleaning and laundries: pickup and delivery stations and self-service," respectively.

Why does this matter? All building codes focus on ensuring the health and safety of a building's occupants. The purpose of building codes does not include quantifying the inherent value of your dirty laundry versus data sitting on a computer server. What is considered "mission critical" by you and a client may not be shared by the authority having jurisdiction (AHJ). While there are certain exceptions, such as designated critical operations areas (DCOA) as defined by Article 708: Critical Operations Power Systems (COPS) of NFPA 70: National Electrical Code (NEC), code considerations typically don't extend beyond the health and safety of a building's occupants.

Figure 1: Central offices (CO) and data centers have similar mechanical, electrical, plumbing, (MEP) infrastructure and associated hazards. This photo is a large, central DC power supply that provides power to telecommunications equipment with a CO. It isWhile the IBC is a far-reaching code encompassing structural, sanitation, lighting, ventilation, and several other areas, life safety considerations in mission critical environments is an important area of focus. The applicable code is NFPA 101: Life Safety Code, which has a more detailed perspective than IBC and is limited to life safety. Similar to the IBC, NFPA 101 is an occupancy-based code. NFPA 101 broadly categorizes occupancy types into the 12 following categories:

  • Ambulatory health care
  • Assembly
  • Business
  • Educational
  • Day care
  • Detention and correctional
  • Health care
  • Industrial
  • Mercantile
  • Residential
  • Residential board and care
  • Storage.

The formal definitions for each of these categories can be found in Chapter 6.1 of NFPA 101. Each of these categories is characterized by the quantity and type of occupants, the type of hazards to which they may be exposed, and the factors that affect the ability to safely egress those occupants out the building in the event of a fire. Interestingly, unlike IBC, NFPA 101 does not define a specific occupancy type for data centers (or self-serve laundromats, for that matter). This does not mean that NFPA 101 does not apply to data centers. Remember that NFPA 101 is not a prescriptive cook book and requires a certain amount of interpretation to apply it properly. 

Is a data center a business or an industrial occupancy?

There can be uncertainty regarding the occupancy-type classification for data centers. NFPA 101 defines an industrial occupancy as "an occupancy in which products are manufactured or in which processing, assembling, mixing, packaging, finishing, decorating, or repair operations are conducted." This broad definition would not seem to apply to data centers. However, "telephone exchanges," which also are defined as a Group B Business Occupancy under IBC, are instead specifically defined as an industrial occupancy type under the Annex Section A. of NFPA 101. While this annex material is intended to be informative and not part of the base requirements of NFPA 101, it is the most definitive interpretation that most AHJ's will have immediate access to.

Historically, a telephone exchange consisted of numerous human operators manually connecting calls with telephone switchboards-similar to a modern call center. However, modern telephone exchanges/central offices are quite different from that historical definition and do not look much different from a typical data center (see Figure 1). So while the IBC makes a clear distinction between "telephone exchanges" and "electronic data processing," the basic functionality, occupancy, and characteristic hazards for these two different uses would seem to be similar in a modern context. By extension, it would be reasonable to assume that if NFPA 101 defined modern telephone exchanges as an industrial occupancy, that classification should also apply to mission critical data centers. Ultimately, that determination is at the discretion of the AHJ.

The primary question is why would there be a difference in a data center's occupancy classification between the IBC and NFPA 101? Without a clear definition, it is debatable as to what a data center is per NFPA 101. Without such guidance, the primary consideration should be an assessment of what occupancy patterns and characteristic hazards are present in a data center environment. Mission critical data centers are characterized by:

  • Unusually high power densities-can easily be more than 100 W/sq ft in the "white space" where the physical server equipment is located, necessitating top-of-row busduct and other similar electrical distribution equipment
  • Onsite energy storage in the form of lead-acid batteries and diesel fuel, which can be fire hazards in of themselves when present in sufficient quantity
  • Unusually high air movement/cooling requirements-can be more than 400 cfm/server cabinet in high-density environments
  • Concealed/confined spaces (containerized data centers, raised floors, isolation of hot/cold aisles, etc.) (see Figure 3)
  • The need for single-shot, total flooding clean agent fire suppression systems that require compartmentalization to function properly in lieu of traditional water-based fire suppression systems
  • The need for redundant mechanical, electrical, and plumbing (MEP) infrastructure to ensure continuity of service
  • A relatively low headcount as compared with traditional business occupancies, with the occupants often clustered in one particular portion of the facility
  • The need to restrict access to the facility to only authorized personnel for security reasons.

Again, the purpose of NFPA 101 is to mitigate risks associated with safely evacuating the occupants of a building in the event of a fire. The primary consideration should be an analysis of "if" and "how" each of these factors impacts the NFPA 101's ability to mitigate those risks, and based on that analysis, which occupancy type provides the most appropriate level of safety for the occupants.

While the generic definition of an industrial occupancy might not seem to be the most appropriate description for a data center, NFPA 101 also lists a "special purpose" industrial-occupancy subset that is described as an industrial occupancy in which ordinary and low-hazard industrial operations are conducted and characterized by a relatively low density of employee population, with much of the area occupied by machinery or equipment. This particular description might be a better fit for most data center environments where the white space and supporting mechanical, electrical, and similar unoccupied back-of-house rooms dominate the overall composition of a facility.

Figure 2: This is a photo of an uninterruptible power supply (UPS) battery string with over 50 gallons of electrolytes. Special ventilation for this installation is required per the International Fire Code (IFC).Although not incorporated as a reference standard in NFPA 101-2015, NFPA 76: Standard for the Fire Protection of Telecommunication Facilities supports this occupancy categorization. The special-purpose industrial-occupancy subset does allow a significant reduction in the egress requirements for a facility, but that ability to reduce life safety provisions and associated costs should not be the primary consideration when selecting this particular occupancy type. Before reducing life safety features, a risk analysis should be performed to confirm that this is the appropriate course of action.

In some cases, the data center might be incidental to the primary function of the building (i.e., a small server room in a commercial office building), which would allow it to be classified as part of the larger business occupancy. In other cases, it might be exactly the opposite (i.e., a network operations center within a large containerized data center). While incidental uses are discussed under NFPA 101's "Multiple Occupancies" section, there is no prescriptive-area-ratio threshold in NFPA 101 to determine if a usage is "incidental."

The AHJ may, in some cases, classify the facility as a multiple-occupancy building (part business and part industrial occupancy) that necessitates a multiple-occupancy designation. In these cases, the most restrictive requirements would apply if no physical separation exists, as described by NFPA's separated occupancy provisions

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