BY RONALD R. SPADAFORA
An atrium (plural, atria) is a large open space, at least three stories high and with a glazed roof. Often, it is positioned just beyond the main entrance doors within a larger multistory building. Atria are a popular architectural design feature because they enhance the perception of light and space within structures. Basically, an atrium is defined by building codes (such as the International Building Code) as an opening connecting two or more stories other than enclosed stairways, elevators, hoistways, escalators, plumbing, electrical, air-conditioning, or other equipment, which is closed at the top and not defined as a mall.
Buildings with atria, however, can be dangerous for occupants in a fire. A large, unenclosed shaft that extends upward through multiple floors is contrary to fire safety, which asserts that compartmentation is required to limit the spread of fire and smoke from the point of origin. The base of the atrium is especially vulnerable. Potentially, a fire at this location can fill the shaft with smoke and allow fire to spread rapidly from floor to floor. Occupants using escape routes within the atrium space during fires may not reach an exit. Fire protection systems and firefighting concerns are two important aspects of atria design, because a fire in a noncompartmented structure has the potential to rapidly grow and spread, transporting heat, smoke, and toxic gases throughout the area (Figure 1).
ATRIA TYPES
Atria can be categorized based on the amount of “openness” between the floors and the atrium.
Fully open. All floor levels are open to the atrium space. This is not code compliant—a maximum of three levels are permitted to be completely open to the atrium. This type of atrium is extremely dangerous for firefighters. The greater the interconnection between the atrium and adjacent spaces, the greater the likelihood that fire and smoke originating at the atrium base level (or any level, for that matter) will spread through the shaft to other parts of the building. The atrium base level may have a functional use (e.g. dining area, lounge, reading, retail stores, kiosks).
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| (1) The New Academic Building at the Cooper Union in New York City has an innovative central atrium to provide a “vertical campus.” Its expansive main inner staircase will pose fundamental access problems for firefighters during emergency evacuation when hundreds of students and instructors use it. Rising to the full nine-story height of the building, this fully open atrium is spanned at various floors by sky bridges. (Photos by author.) |
Partially open. Some of the floor levels above the atrium base are open to the shaft, while the remaining areas above are closed off by fire-rated or code-recognized special barriers such as tempered glass with closely spaced sprinklers on both sides of the glass. The barriers are designed to stop smoke spread, not fire. The bottom level of the atrium may have a functional use.
DESIGN FEATURES
Atria present the fire service with some unique design concerns. An open flue-like area within the building that interconnects a large number of floors compromises the principle of compartmentalization. Current building codes attempt to deal with this problem by specifically requiring a complete sprinkler system, mechanical smoke system using fans, emergency power, and specific fire barrier criteria, which will be described in greater detail below. Many buildings across the United States predate these codes or were built without any code. Therefore, the atria you will encounter may attempt to mitigate these dangers by installing a combination of active and passive (built-in) smoke control systems, automatic and manual roof vents, automatic sprinkler systems, standpipe systems in enclosed stairs with hose for fire department use, smoke/heat detectors and audible/visual alarms, automatically controlled fire doors (passive system), fire partitions/separations (passive), draft curtains (passive) sufficient means of egress, illuminated exit signs, low-level exit signs, an abundance of portable fire extinguishers, and a specially designed ceiling to create a smoke reservoir (passive).
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| (2) The New York Marriott Marquis Hotel atrium clearly has an open, vertical flue design. Room and elevator occupants are all potentially vulnerable should a fire originate in this area or spread into this uniquely expansive hotel atrium. |
For some atria, one fire control approach is to install sprinklers under canopies on the atrium floor; another is to install fixed water spray nozzles on the lower floors for extinguishing fires at the base floor of the atrium.
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| (3) Roof vents are just one of the many fire protection features of an atrium. |
High ceilings dramatically complicate and potentially delay early smoke and heat detection. Although smoke and heat detectors should be placed at the highest ceiling level, devices that can identify smoke near occupied floor levels and potential fire sources are the best. Smoke detectors should be in ceiling spaces surrounding the atrium as well as within the atrium enclosure itself. These areas include low-level spaces within balconies, alcoves, corridors, and lobbies. Projected beam smoke detectors are often used to monitor for smoke in the atrium and to activate a smoke-management system.
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| (4) A key smoke management goal during a fire incident is to keep the smoke layer an adequate distance above the highest atrium balcony. |
Atria design breaks with conventional building configuration, but key fire and life safety elements (e.g., escape routes, smoke control, and firefighting provisions) must still be addressed. Emergency egress is incorporated into the building’s fire protection/safety plan. Smoke control strategies should also be a part of initial ventilation concepts. Firefighters stationed in-house (trained employees) as well as external (your friendly neighborhood fire department) must be provided with the technical expertise to manage and control a potential large-scale fire situation.
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| (5) Supply fans are hidden behind this bamboo enclosure, located at the lowest level of the Conrad New York hotel atrium. |
Successful egress planning recognizes the importance of unaided and aided occupant movement from a fire to a protected exit. The routes taken must remain tenable throughout the evacuation process. Unfortunately, in an emergency, people in unfamiliar surroundings tend to use the way they entered as their sole exit route. Unlike the occupants of office buildings, who can be trained to use alternate exits through fire drills, visitors will generally use only the way they came into the building as a clear egress path. National Fire Protection Association (NFPA) 101, The Life Safety Code, requires an engineering analysis to demonstrate that smoke will be managed for the time needed to evacuate the building. The study must prove that the smoke layer will be maintained above the highest unprotected opening to the adjacent atrium space for a reasonable amount of time necessary to safely evacuate the building’s occupancy load. For a hospital or nursing home occupancy, which would employ shelter-in-place provisions, smoke control performance must be maintained to protect life indefinitely.
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| (6) Tandem exhaust fans are spaced approximately 20 feet apart along the atrium ceiling. |
GENERAL FIRE PROTECTION REQUIREMENTS
Model building code fire protection requirements for atria have been established to protect occupants and minimize the risk of fire spread. Throughout the United States, the authority having jurisdiction (AHJ) at the state and local levels has incorporated many if not all of the following important life safety features:
- Fire barriers (one-hour fire rating) separating the atrium from the rest of the building.
- Nonfire-rated barriers if sprinkler heads are on both sides of barriers.
- Sprinkler system required for the entire building.
- Restricted use of combustible materials at the atrium base floor.
- An active or passive (built-in) smoke control system designed to keep ceiling smoke layer at least six feet above the highest level means of egress walking surface for at least 20 minutes.
- Mechanical exhaust equipment that the fire service will be able to operate.
- Maximum travel distance of 200 feet from within the atrium to the exit.
- Active smoke control systems (sprinkler head/water spray nozzles and supply/exhaust fans) activated by smoke/heat detection or sprinkler water flow.
- Active smoke control systems must also allow manual operation.
- Standby power must be provided for active smoke control systems.
- Walls and ceilings within the atrium must have a Class A or Class B interior finish rating.
FIRE PROTECTION ENGINEER GOALS
A fire generating smoke within an atrium will accumulate at the ceiling level and create what is known as a smoke layer. The size of this smoke layer is important when fire protection engineers design smoke management systems. Their goal is to keep the smoke layer at the uppermost level of the ceiling, well above the highest balcony or walking surface. This will limit the amount of smoke occupants will encounter while exiting their floors.
To effectively prevent the products of combustion from moving downward, design plans generally need to incorporate exhaust fans large enough to remove the smoke at a rate at least equal to the rate of smoke production. The fans’ sizes and required exhaust rates may, however, be significantly less than the rate at which the fire is producing the smoke. In this situation, the smoke layer below the ceiling could descend well below the highest floor/balcony level, endangering occupants with the accumulation of heat and toxic gases, thereby hindering their movement toward available means of egress.
The height of a smoke layer can be controlled naturally or mechanically. Natural venting at the top of the atrium space relies on the buoyancy force caused by the elevated temperatures of the layer of hot gases. Mechanical venting is more positive with regard to the venting rate and less affected by wind than natural venting. Fans along the ceiling are the primary means used to exhaust smoke and other products of combustion from atria spaces. The smoke control system also provides supply fans at the lower levels.
Mechanically exhausting the atrium can lower the pressure inside compared to outside the building. The flow of outdoor air will then enter through openings in the exterior walls. This air flow travels through floor spaces and openings in fire separations into the atrium, thereby isolating smoke the atrium fire is generating. The negative pressure created in the atrium can also prevent smoke from entering vertical arteries, such as stairs and elevator shafts. This action should have positive effects on firefighting operations.
SEPARATING ADJACENT SPACES
Fire separations and stair vestibules are often required to prevent smoke from encroaching on public escape routes. Protected floor spaces require fire separations with a fire resistance rating equal to that of the floor assembly, and openings in such separations require vestibules to prevent smoke entry. If floor spaces have sprinkler heads, unrated fire separations may be permitted in public corridors. Even unrated fire separations, however, must remain intact until sprinklers are activated to prevent the spread of fire and smoke. To maintain the integrity of these types of fire separations, sprinkler heads are sometimes installed (Figure 2).
SMOKE MANAGEMENT
Historically, model building codes have a specifically required rate of smoke exhaust in terms of air changes per hour. Today, however, a prescriptive number of air changes may not be appropriate for modern smoke management designs. Many model codes are therefore converting to a performance-based design approach to smoke management systems. As stated previously, effective smoke management depends on the rapid control of the fire and limiting the quantities of smoke and toxic gases. Fundamental to this objective is the installation of early detection devices and rapid suppression systems. Detectors are best positioned where they can activate quickly. Ideal placement includes balconies, corridors, lobbies, and other spaces with normal ceiling heights.
Fire protection engineers often design their smoke management systems based on an evaluation of actual anticipated fuel loads and heat release rate within the atrium. To determine the appropriate size of supply and exhaust fans, they use the equations in NFPA 92B, Standard for Smoke Management Systems in Malls, Atria, and Large Spaces, 2009 edition. Their main objective is to remove smoke to attain a high level of life safety and minimize property loss. Other goals are to provide a safe and tenable means of egress for building occupants in the event of a fire and an adequate level of visibility for firefighters. A special concern is smoke movement from the atrium to floor spaces, stairs, and elevators where occupants are likely to be exposed. The specific objectives must provide a viable means of egress for occupants with adequate visibility for firefighting and occupant rescue. Smoke temperature and toxicity are studied to ascertain if there is sufficient time for safe egress of occupants.
FIREFIGHTING STRATEGY AND TACTICS
Atria design error is more common when smoke control systems are installed based on only a single fire scenario. In reality, multiple fire situations should be anticipated. For example, if an atrium is used temporarily as an exhibit and showroom venue, this adds a substantial fuel load that was not calculated into the design. Chief officers must be vigilant in their recommendations and guidance to building owners, managers, and agents regarding such ancillary shows. Additional fuel loading should be kept to a minimum to ensure atrium smoke management and other fire protection systems will not be overwhelmed and defeated.
Preplanning is important to enhance building and occupancy situational awareness. What fire protection systems are inside the building, and who is maintaining the equipment? Is there an in-building communications system? Chief officers should ascertain how many street entrances lead into the base of the atrium. Can fire apparatus access these streets? How many hose lengths are required to stretch from the engine to reach areas in lieu of using standpipe outlets?
Additionally, predetermine the maximum floor levels that apparatus ladders can reach on all four sides of the building. Exterior ladder rescue/vent/entry/search (RVES) as well as possible ladder pipe deployment will be essential to successfully complete firefighting operations in a structure containing an atrium.
Small departments should have mutual-aid agreements in place for fires in a building containing an atrium. The potential for fire and the products of combustion to endanger numerous building occupants on multiple floors dictate an adequate response of staffing, apparatus, tools, and equipment. Anticipate the need for multiple rehabilitation and care (RAC) units. Contact outside agencies (American Red Cross, for example) to inquire about their ability to respond to a multiple-alarm fire in an atrium building to provide necessary occupant relocation and creature comforts.
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| (7) The Winter Garden in the World Financial Center in New York City is a three-story glass atrium with resident palm trees. Fire protection engineers and the fire service must consider their fuel load and burning characteristics when evaluating the structure’s fire protection requirements. |
During fire operations, the incident commander (IC) should request the building engineer to respond to the incident command post (CP). The engineer’s expertise regarding the atrium’s smoke management equipment will be extremely helpful. Properly activating fans, vents, hatches, exhausts, and smoke-stop doors will allow the fire service to complete vital rescue and search objectives successfully and safely. The IC should also request floor plans and focus on locating the living quarters and their relationship to means of egress. Note if staircases, elevators (passenger and freight), vestibules, and protected floor areas are not interconnected to the atrium. Formulate strategy and tactics based on the location of the fire and where the fire/smoke is most likely to travel in the occupied areas of the building. Public announcements over building loudspeakers, if feasible, can also be valuable. Conveying to occupants what they should and should not do will not only help protect them but also facilitate firefighting operations.
Chief officers must develop a firefighting strategy to prevent units from operating conflicting hoselines. This dangerous situation can easily occur since atria often are designed with several entrances. Engine company officers operating at a working fire must communicate with each other regarding apparatus placement, point of entry, hoseline stretches, and hose stream direction to enhance safety. Coordinate extinguishment and search/rescue tactics so that firefighters engaged in these tasks do not put themselves in front of operating hose streams or in precarious locations above the fire. Determine the number of staircases that service the atrium and ensure that they are assigned proper designations (Attack/Evacuation) during the fire. In size-up communications, use accurate terminology to describe specifically the correct fire area and where in the building the fire is located. Distinguish between fire in the lobby of the atrium and on a floor balcony above.
Team up first-arriving engine companies. Long hand stretches dictate this policy. Of course, the initial hoseline’s size should be commensurate with the fire’s magnitude. In general, however, use a 2½-inch hose for a fire of unknown size or one that is beyond the capability of a portable fire extinguisher. I strongly recommend a smooth bore nozzle with a minimum 11⁄8-inch tip to attain approximately 250 gallons at 50 psi nozzle pressure. This nozzle will also provide a compact, longer stream and better penetrating power to reach the seat of the fire than would a combination or fog nozzle.
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| (8) Preplans must be formulated to address long and interconnected public walkways. The danger of conflicting hoselines at fires in atria is very real. |
Ladder companies should also team up members to accomplish their goals. Just a few of the duties that will have to be accomplished include outside surveys, exterior RVES, interior firefighting, and expansive searches. Thermal imaging cameras and search ropes are two primary tools firefighters must carry inside the building to aid in finding possible victims, the fire, and fellow firefighters who may become incapacitated during the operation. Ladder company personnel must be thoroughly trained on this equipment. The unskilled use of these two tools can instill false confidence in members and lead to dangerous results. You may need multiple rapid intervention teams (RITs) based on the atrium’s type and dimensions. When warranted by fire conditions, consider positioning a RIT inside the building in an uncontaminated area, to support firefighters working in an immediately dangerous to life or health environment on the upper floors.
Be proactive; call for special units (e.g., rescue, squad, mask service, rebreather, ventilation) to respond for significant fires in buildings with atria. The IC should use rescue and squad companies for specific tasks that complement the engine and ladder companies’ work, such as roof ventilation, wind-control blanket/curtain deployment, and upper floor/stair/elevator searches.
Large-scale fires will demand long-time, labor-intensive operations to bring them under control. Bringing additional self-contained breathing apparatus (SCBA) to the scene will facilitate firefighters in reaching their objectives. Rebreather units use an SCBA that resupplies exhaled air to the user, providing up to four hours of operating time. Firefighters using rebreathers can supplement search operations once the fire has been placed under control and can be especially useful in surveying structure sublevels for high amounts of lingering carbon monoxide.
Positive pressure ventilation (PPV) is yet another important tactic to consider when battling fires in atria. Brought to the scene by ventilation control units, PPV fans can be strategically positioned to control and channel smoke and the products of combustion. Coordinating the use of PPV with the movement (sheltering) or evacuation of occupants will enhance life safety operations. Box fans (smoke ejectors) can also help to improve interior conditions by removing smoke and toxic gases from the building.
At fires in building atria, the number of occupants requiring reassurance and assistance may overwhelm the IC. Numerous phone calls to 911 and the communications office and messages relayed to the fire scene will place a heavy burden on members at the CP trying to record and manage the required searches. The IC must ensure dedicated personnel are monitoring this information; a communications unit is ideal for this task. Units listed on a command board and operating inside the building can be coordinated to check on all distress calls received. Additional radio frequencies (channels) may also prove useful in organizing company activity. Consider placing chief officers not directly responsible for tactical operations on a command channel. This will enhance strategic decision making and help reduce some of the radio traffic on the primary tactical channel. Also, it may be beneficial for companies performing specialized tasks to have their own channel (secondary tactical) to transmit and receive vital information without being “stepped on” by personnel carrying out conventional duties.
The ranking EMS officer should also be at the CP to aid the IC in determining the number and severity of all occupant injuries as well as the medical status of firefighters. Victim tracking is another critical assignment for this EMS officer. If possible, the IC should acquire all incident death/injury statistics while he is still on scene. This information is important when required by superiors and the media. Knowing to which hospitals victims have been transported is also extremely helpful to fire marshals who may want to interview people who have knowledge of the cause and origin of the fire.
An atrium allows the builder to take advantage of available sunlight and provide enhanced ventilation throughout the occupied area. However, it also provides a horizontal and vertical pathway for fire and the products of combustion to spread rapidly, endangering occupants who may be trapped in hallways, corridors, passageways, vestibules, stairs, and elevators. Chief officers should review their AHJ regulations and standards pertaining to fire protection systems required within this green construction (daylighting) feature. Preplanning designed to emphasize and understand potential life safety and fire extinguishment obstacles will enhance operational effectiveness. Conduct familiarization drills and supplemental training in firefighting tactics for members to ensure your responding firefighters are prepared to perform professionally and safely.
REFERENCES
Bastings, D. Building Research Association of New Zealand. BRANZ Study Report – Fire Safety in Atrium Buildings, No.15 (1988). Date Retrieved: July 24, 2011. www.branz.co.nz/cms_show_download.php?id=82a763017043e836229d23f5aae1ee2920b585c4.
Chew, M.Y.L. and P.H Liew. “Smoke Movement in Atrium Buildings,” International Journal on Engineering Performance-Based Fire Codes. Volume 2, Number 2, 2000. 68-76.
Gritch, Todd AIA, ACHA and Brian Eason, AIA. National Institute of Building Sciences. Building Envelope Design Guide – Atria Systems. Last updated: June 7, 2010. Date Retrieved: July 18, 2011. www.wbdg.org/design/env_atria.php.
Klote, J.H. and J.A. Milke, Principles of Smoke Management, Atlanta: American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), 2002.
Klote, Dr. John H., P.E. and Douglas H. Evans, P.E. A Guide to Smoke Control in the 2006 IBC, Illinois: International Code Council (ICC), Inc., 2007.
Lougheed, G.D. National Research Council Canada, Basic Principles of Smoke Management for Atriums, Construction Technology Update No. 47, December 2000. Date Retrieved: July 14, 2011. www.nrc-cnrc.gc.ca/eng/ibp/irc/ctus/ctus-n47.html.
National Fire Protection Association. NFPA 92B, Standard For Smoke Management Systems in Malls, Atria, and Large Spaces (2009 ed.). NFPA: Quincy, MA. 2009.
National Fire Protection Association. NFPA 101, The Life Safety Code (2009 ed.) NFPA: Quincy, MA. 2009.
Sharry, J.A., “An Atrium Fire,” Fire Journal. National Fire Protection Association (NFPA): Quincy, MA, 1973, 39-41.
Siemens Building Technologies, Inc. Smoke Control System Application Guide, 125-1816 Rev. 8/00 USA: Siemens Building Technologies, Inc. August 2000.
Spadafora, Ronald R. “An Introduction to Green Building Construction,” WNYF, Third Issue, 2008, 20-24.
Spadafora, Ronald R. “Green Building Construction and Daylighting: A Chief Officer’s Perspective,” Fire Engineering, October 2010, 75-90.
Spadafora, Ronald R. “The Fire Service and Green Building Construction: An Overview,” Fire Engineering, January 2009, 63-78.
Tamura, G.T. National Research Council Canada, Smoke Management in Atria, NRC-IRC publications. Date modified: May 5, 2009. Date Retrieved: July 25, 2011. www.nrc-cnrc.gc.ca/eng/ibp/irc/cp/fir2.html.
United States Fire Administration (USFA). National Fire Academy (NFA). Building Construction: Atrium Fire Protection Requirements. No. FP-2009-23. June 9, 2009. Date Retrieved: July 30, 2011. www.usfa.dhs.gov/downloads/pdf/coffee-break/cb_fp_2009_23.pdf.
RONALD R. SPADAFORA is a 33-year veteran of the Fire Department of New York and is an assistant chief. He teaches at both the graduate (emergency management) and undergraduate (fire science) level as an adjunct professor at Metropolitan College of New York and John Jay College respectively. He is the senior instructor for Fire Technology Inc., as well as an editor and frequent contributor to FDNY’s WNYF magazine.
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