By Gerald Tracy
More people “die from smoke than from direct exposure to fire.”(1) This reality has prompted the fire service to revisit, refine, and revamp “smoke skills” and ventilation protocols for their standard operating procedures (SOPs). This is particularly important with tall and large buildings because they have the potential for a significant loss of life influenced by the magnitude of the structure and occupancy type.
Residential occupancies have the highest percentage of fires, with cooking being the most common cause.(2) Structures built and inhabited as residential occupancies are considered compartmentalized, following the codes and standards of design and fire protection separating each apartment. The expectation is that a fire will be confined to a single unit because of the type of construction and required passive fire protection elements of fire rated walls and doors with self-closing mechanisms. The most common failings in residential structures are when people exit their apartment in a fire and leave the door open, providing a path for toxic smoke to flow into public corridors, stairs, and elevator shafts. Heated fire gases flow out through the upper layer of the open door frame, and air (providing oxygen) flows in below that layer. This provides more oxygen to sustain combustion for a fuel-controlled fire rather than transitioning to a ventilation-controlled or vent-limited fire.
People self-evacuating from other than the fire apartment have become victims, often resulting in a multicasualty incident, similar to the Twin Parks fire in the Bronx, New York, in 2022.(3) Residential high-rises, other than hotels, are not typically designed with a smoke exhaust system that will limit migration or offer safe refuge in public corridors, stairs, and elevators. These tragic events are occurring more frequently because of the lack of fire safety awareness or instructions provided to a resident population that is constantly changing.
Depending on the magnitude of a situation and resources available, the incident commander (IC) must make and prioritize decisions based on the life hazard. When staffing and equipment are available, the fire service must implement a plan of action for smoke management and control in these types of structures. This means applying “smoke skills” to begin clearing egress routes and perform search, rescue, and fire extinguishment.
“Urban Hub Developments”
Mixed-use occupancies in tall and large buildings are becoming more common in the urban landscape. They provide living quarters with access to all the facilities and services that complement a lifestyle of comfort and convenience and are close to places of employment. They are often referred to as “Urban Hub Developments”(5) and accommodate several commercial tenants. From the standpoint of fire and life safety, each occupancy poses a different fire problem based on fuel load, how the fuel is stored and concentrated, if the occupancy is compartmentalized, oxygen availability, and access and egress for the occupants and fire and rescue operations.
Focusing on fire operations, what will be the fire dynamics and expected life hazard in each of these occupancy types? Can the fire service rely on existing smoke control systems, or will each occupancy have a proprietary system? In either case, the fire service must be aware of and have familiarization with and training on their function and limitations, if any.
The fire service must be ready and able to implement “smoke skills” to augment a system deficient or nonexistent when necessary. This entails disciplines and protocols that limit migration with door controls, smoke blockers, and portable fans to pressurize stairs. These same fans can be used to sequentially vent smoke from specific floors, spaces, and the entire structure.(4)
The fire service must know when it is prudent to instruct occupants to “shelter in place.” This strategy lessens the resources needed for rescue, placing priority on fire suppression and smoke management.
Businesses in “Urban Hub Developments” range from corporate to finance, law, government, health care, academia, and hotels. The fire problem and threat to life safety will be different in each occupancy type. Office buildings can have large open floor plans, sometimes on a raised floor, and many small office spaces and conference rooms accessed by a labyrinth of foyers, paths, and corridors. The fire dynamics, smoke migration, and operational tactics will be quite different in each occupancy.
In the past decade, there have been many research studies on fire dynamics that provide conclusive evidence that ventilation principles and practices for tall and large buildings require examination and, in some cases, need improvement.(6) Fire dynamics and smoke migration in Type I (Fire-Resistive) construction is quite different from Type III (Ordinary or Brick and Joist). Migration will seek a flow path with pressures lower than the space, with increased pressures from fire and expanding gases, mostly smoke. Seasoned firefighters and chief officers with experience can, for the most part, anticipate where smoke will flow based on the occupancy type. Many departments/brigades have formulated their SOPs to assign fire units/teams to areas of the building that are likely to become “smoke logged” and where the threat to life may be present.
Lessons from Grenfell Tower
When there is a great loss of life, there will be a call for review as to the circumstances that contributed to the deaths. Those with interest or motivation will be the surviving relatives, insurance organizations, and government agencies responsible for the enforcement of codes and life safety. The fire service globally should be aware of the scrutiny and inquiry the London Fire Brigade endured from the Grenfell Tower tragedy that resulted in 72 fatalities in June 2017. Their policies and procedures were in question as well as the qualification and competency of Command.
This fire was unique in that fire had communicated from a fourth-floor apartment window to involve the façade of metal cladding that included combustible insulation in its fabricated assembly. The critical factor of the assembly was an air gap between the exterior metal sheets and insulation. This gap accelerated fire extension vertically and horizontally around the entire structure. The heat and flame front caused windows to fail and extended into other apartments above.
To compound the situation, the structure was built with a single staircase with no secondary means of escape. This was permitted because the public space on each floor to access each flat was designed with a smoke exhaust scheme and system to purge smoke from that space and keep the stair free of contamination. It was an approved system designed to handle smoke generation from a single flat/apartment. Because there were multiple flats on fire, the smoke overwhelmed the system. Thus, that singular means of escape became highly contaminated with smoke.
The fire progression was fast and furious, with people being overcome in the stair shaft and many trapped in their flats. The strategy of shelter in place became a death warrant. The London Fire Brigade was criticized for that decision, as it was believed that the building was designed with all the features of life safety required by the existing codes and standards. The inquiry revealed the lack of oversight by code officials and the contractors, who had installed the cladding that would not pass scrutiny on performance after being exposed to fire. The London Fire Brigade would have no knowledge of that.
You can bet that if a multiple-fatality event due to smoke inhalation were to occur in North America, the strategy and tactics employed would be scrutinized. A major issue would be if and when a smoke control strategy was implemented and if it could be justified as “best practice.” It could be determined in the judgment of a court inquiry or post-incident investigation that best practice had not been applied based on the research made available to the fire service. Those paying attention to the research being conducted by institutions such as NIST, UL, and the ATF are becoming more aware of fire dynamics, flow paths, smoke migration, and techniques to manage and control smoke.
Many departments/brigades have had to adopt a methodology that rationalized and acknowledged those tasks and actions on the fireground that influence fire development and smoke migration. Acclimatization may require a departmentwide attitude adjustment because the established practices may have become antiquated or been considered detrimental in certain circumstances. It is my contention that the ventilation practices brought forth for tall buildings were proven appropriate for fires in structures built of Ordinary Construction (Type III) and not Fire Resistive (Type I).(7) Still, many departments/brigades are not aware of this research, and their frequency of response to fires in Type I structures is rare.
Expect the Unexpected
The fire service has learned to expect the unexpected at fires in tall and large buildings. It is not uncommon to experience window failure that would not only provide more oxygen to a fire but become a blowtorch in the face of firefighters entering the space from the stair shaft or main entrance door of the apartment. The results of research on fire dynamics specific to wind-impacted fires provide visual cues to identify wind as a factor on arrival and what to look for while conducting a visual size-up. The research has prompted departments to adopt alternate tactics appropriate to the type of building, occupancy, and floor plan with public corridors, layout of apartments, and exterior balconies if present.(8) Smoke skills are incorporated into these tactics as well as methods to effect fire extinguishment.
The Fire Department of New York (FDNY) has adopted the use of fire curtains to be draped over a failed window to allow a direct attack into the fire apartment. A high-rise nozzle designed by an FDNY firefighter can be used from a vantage point to direct water into a fire area where curtains are ineffective. Breaching a wall from an adjoining apartment or approaching from an adjoining balcony is another option.
Reports from the fire floor and sector are vital to challenging fire conditions, uncontrolled evacuation, and indication of a wind-impacted fire. The IC must be made aware of any life hazard in the stairs and fire sector. The tactic implemented must also be reported to the IC to ensure resources are made available to maintain the effort of suppression and search. The IC is responsible for ensuring resources will be forthcoming to rotate and relieve those units and teams engaged in battle.
The methodology of smoke skills should be well-defined in department SOPs. Each individual is responsible for those actions that can influence smoke migration, because “smoke kills.”
References:
1. “House Fires: The Fatal Danger Beyond the Flames.” Cleveland Clinic, 3 Nov. 2021, bit.ly/40KDpNT.
2. “Fires by Occupancy or Property Type.” NFPA, 2022, bit.ly/3AGA4VG.
3. Singhvi, Anjali, et al. “The Chain of Failures That Left 17 Dead in a Bronx Apartment Fire.” The New York Times, 8 July 2022, nyti.ms/40KkD9r.
4. Leeb, Frank. “Sequential Ventilation.” WNYF, 2022, bit.ly/4er4edd.
5. Tracy, Jerry, et al. High-Rise Buildings: Understanding the Vertical Challenges. Fire Engineering Books, 2023.
6. NIST–UL–ATF:
• Kerber, Stephen. “Evaluation of Fire Service Positive Pressure Ventilation Tactics on High-Rise Buildings.” National Institute of Standards and Technology, 2007, tsapps.nist.gov.
• “Research Projects – Ventilation.” Fire Safety Research Institute, bit.ly/40G31eX.
• Rosenfeld, Derek. “Ventilation Flow Paths and Fire Growth: A Review of Recent LODDs.” Fire Engineering, 8 Apr. 2014, bit.ly/4hXgntw.
7. “NFPA 220 Standard on Types of Building Construction.” NFPA, 2024, bit.ly/4evXZVF.
• Type I (Fire-Resistive): Uses fire-resistant materials.
• Type II (Non-Combustible): Uses non-combustible materials.
• Type III (Ordinary or Brick and Joist): Uses brick and joist construction.
• Type IV (Heavy Timber): Uses large wooden beams.
• Type V (Wood-Frame): Uses wood framing.
8. Leeb, Frank. “Coordinating Ventilation with Suppression.” Fire Engineering, 1 May 2019, bit.ly/3YQ3clc.
Gerald Tracy retired as battalion chief from the Fire Department of New York (FDNY) after 31 years. He was instrumental in refining and improving policy and procedures for the FDNY as well as developing numerous training programs. He has published several articles in Fire Engineering and WNYF. He was the catalyst to the research conducted by NIST, UL, and NYU Polytechnic Institute on smoke management and fire behavior in high-rise buildings, emphasizing research with wind-driven fires. He was a keynote speaker at FDIC 2007 and received the Tom Brennan Lifetime Achievement Award in 2016. He is a coauthor of the book High-Rise Buildings: Understanding the Vertical Challenges (Fire Engineering Books).
