In reviewing mission-critical data centers under construction, both during the submittal phase and during on-site inspections, I’ve found that the single most misunderstood issue is penetration firestopping. Fire and smoke containment requires fire-rated barriers and smoke barriers at important locations. Because every penetration into these barriers is a potential breach that compromises life-safety measures, everyone involved must understand this vital issue.
Penetration Firestopping Simply Defined
Fire-rated barriers include fire walls, fire partitions, tenant-separation walls and floor/ceiling assemblies. Any penetrations into or through them (by pipes, conduits, electric cable trays, busways, etc.) must be installed such that they won’t affect the barrier’s resistance to burn-through, temperature-induced combustion, smoke penetration and water seepage. The only way to do so is to install the penetrating item in accordance with the building code or a national testing agency’s penetration-firestopping system. A widely known resource for tested firestopping systems is UL’s “Fire Resistance Directory,” which contains thousands to choose from.
Penetration firestopping in data centers is more complicated than in other building types: First and foremost, per the NFPA 75 code, a water barrier (defined as a “W” rating) is necessary for the “protection of information technology equipment.” Second, data centers tend to have more large penetrations from room to room than other building types (the best examples being penetrating ductwork and the wide cable trays that start in UPS battery rooms, travel into the electric rooms and end in the server rooms). Third, servers are moved from time to time without close-ins (on several inspections to some older facilities, I observed a series of rectangular holes up high in several rated walls, aligned through several rooms; they appearing to be openings for electric-cable trays that had long since been removed).
Required Ratings and Designations
Three common explanations that I give on a site inspection are that fire caulk is not a penetration-firestopping system, it’s only one component of a system; wires protruding from a rated wall must be housed in an approved conduit or sleeve; and most if not all penetrations into fire barriers must be installed per a tested firestopping system.
As you’d expect, penetration-firestopping systems come with lists of required materials, sizes and thicknesses for each component (such as maximum pipe diameter, conduits being of steel or copper, and minimum floor-slab thickness), but they also typically have established ratings of F, T, L and W earned during fire testing. The project architect must establish the parameters that code requires (by listing them in the project specifications) and review the project general contractor’s submittal as a double-check, but it’s up to the GC to submit to the architect the proposed firestopping systems and then ensure that they’re installed per the testing agency’s many requirements.
The abovementioned ratings, simply explained, are as follows: F is the penetration-firestopping detail’s burn-through time measured in hours (it must at least match the rating of the wall or floor being penetrated). T is the burn-through time and temperature in hours (which must also at least match the wall or floor being penetrated); it’s designed to avoid ignition of flammable items residing near the penetration caused by the intense heat coming from a fire in an adjacent space. L is the smoke penetration allowed in cubic feet per minute per square foot of opening (with 5 cfm/sf usually being the maximum allowable); it’s intended to limit the amount of oxygen-depleting smoke that could travel through the penetration. And W, as previously mentioned, is the water leakage at the rated floor or up to 3' high on a rated wall as tested by UL 1479, which is designed to prevent water (from an activated sprinkler, firefighter’s hose or ruptured pipe) from damaging equipment in rooms on the floor below.
In addition to the above ratings, building codes usually require that any exposed materials, sealants and finishes have a flame-spread index (FSI) of 25 or less and a smoke-developed index (SDI) of 450 or less. Plus, the project architect also may set a maximum level of volatile organic compounds (VOCs) allowed for each material, with sealants typically being limited to 250 grams/liter. The general contractor must submit all of these data to the project architect during the submittal phase, before a penetrating-firestopping system’s installation, and then perform the installations per the reviewed system’s requirements.
Selecting a System
To help select a conforming system, UL has developed a nomenclature for its penetrating-firestopping systems (system number “C-AJ-1473,” for example). Because all systems may need to meet the project spec’s F, T, L and W requirements as well as VOC, FSI and SDI limits for fire caulk and other materials, the best selection process is to first look for a system that combines the penetrant (e.g., non-metallic pipes) and the assembly being penetrated (e.g., one-hour-rated drywall), then verify that the system meets the seven aforementioned designations.
Regarding the W rating, it’s important to note that some fire caulk is water soluble. So, although it may be tested to resist fire, time/temperature and smoke for, say, two hours, it won’t prevent water from penetrating the firestop barrier. A system that fails a required W rating could allow water to pour down onto equipment a floor below; if the equipment happens to be servers or UPS batteries, this failure could potentially cripple a mission-critical data center.
For small and midsize penetrations, such as metallic pipes that are less than 6" in diameter, the penetrating-firestopping detail sometimes calls only for fire caulk, slag wool or rock wool in the annular gaps (annular is defined as ring shaped, but it also commonly applied to gaps of any shape) and a minor list of other requirements. Fire caulk—typically red but also available in grey and white—is an intumescent material that expands exponentially when exposed to heat (to about 35 times its original size), creating a more robust seal against flame, heat and smoke.
A penetrating conduit (or pipe) and a penetrating sleeve, of course, have different firestopping properties: a conduit is a continuous enclosed container that won’t readily transmit fire, smoke or water, whereas a sleeve is an open system that will transmit those elements if firestopping material is improperly installed.
So, although a firestop system may be unnecessary for small poured-in-place steel or copper conduit in a concrete floor, a core-drilled sleeve will need firestopping at the open gaps inside it (between the sleeve’s inside face and the conduit’s outside face) as well as around it at the floor or wall it’s penetrating. The annular space in a maximum 6"-diameter sleeve can either be filled per an approved firestopping system or be filled with concrete, mortar or grout for the full thickness of the concrete floor. This requirement is meant to ensure, among other things, that the sleeve size and fill material will maintain the poured assembly’s F, T and L ratings, that the system’s fire caulk will meet the W rating, and that the fire caulk and other components will meet the VOC, FSI and SDI requirements.
For large and irregular penetrations—most frequently, cable trays—an approved penetration-firestopping detail is usually too large to pass a fire test with just fire caulk and mineral wool. Products such as intumescent firestop pillows and intumescent firestop bricks can fill large penetrations in rated walls, but they require careful and uniform placement on top of the tray’s conduits to fill in any large hole them. All too often, however, use of these products misses two critical points: first, the need to employ fire caulk at all gaps between and around the pillows or bricks, and second, the need to shield the pillows or bricks with an outer covering (a wide intumescent strip or wire mesh) to protect them from unwitting future breaches during maintenance, repairs or renovation. This protective covering, when breached, provides a visual signal that the penetration firestopping may have suffered damaged and needs restoration.
The Submittal Process
The proper process for creating the penetration-firestopping submittal begins with the project’s electrical, mechanical and plumbing subcontractors: each one sends the project GC the penetration-firestopping systems they intend to use for the penetrations they’ll make into rated assemblies. The GC gathers the systems (usually around 5 to 10 different systems), reviews them for compliance with the project specs, adds corrections or comments, and sends them to the project architect for another review.
Unfortunately, I too often find most penetration-firestopping submittals usually comprise the same things the subcontractor uses for every job, including an overabundance of UL system detail sheets—usually in a 50- to 100-page document—and mostly depicting various penetrating conditions that the project doesn’t involve. On the other hand, I too often receive penetration-firestopping submittals that have only 1 system indicated even though 5 to 10 systems are typically necessary. To the architect, receiving too many or too few systems is a red flag indicating that the GC just forwarded the standard subcontractor pack without reviewing the details for applicability or compliance.
Additionally, and most importantly, I find that these firestopping submittals seldom include a “penetrations product schedule” (usually called for in the architect’s project-spec section 078413), which indicates critical information such as each penetrating item (such as a busway or 4" metallic pipe), the construction it’s intended to penetrate (such as drywalled stud wall or concrete floor), the proposed penetration-firestopping system number and confirmation that each complies with the seven penetration requirements. In this way, the architect knows which system number the GC and its subcontractors intend to use for each condition and can quickly understand and check them against the project specs.
The best project specifications require the GC to install a preprinted label (metal or plastic, self-adhering or mechanically fastened) within 6" of each penetration-firestopping condition. The approximately 3" by 6" labels should at a minimum contain the following information:
- The words “Warning—Penetration Firestopping—Do Not Disturb. Notify Building Management of Any Damage”
- The penetration-firestopping system number
- The general contractor’s company name, address and phone number
- The installer’s personal name and company name, as well as the date installed
With a chain being only as strong as its weakest link, an improperly installed or missing penetration-firestopping system can weaken or destroy a wall’s or floor’s fire resistance. With life safety being the most critical element in a mission-critical data center, special care is necessary to ensure the integrity of each fire barrier.
About the Author
Dean Ventola, RA, NCARB, LEED AP BD+C, is the Director of Construction Administration at DVA Architects in Gaithersburg, MD, a nationally prominent mission-critical data center architect.