The National Fire Protection Association (NFPA) defines high-rise buildings as buildings where the floor of an occupiable story is over 75 feet above the lowest level of fire department vehicle access.

Their height and high occupancy present significant challenges for fire protection. Fires are typically out of reach of ground-based fire department ladders, and they can often have a large number of people inside, making evacuation challenging. Unchecked, the vertical nature of high-rise buildings causes fire and smoke to spread rapidly through stairwells.

These factors necessitate carefully designed fire protection measures by expert fire protection engineers to prevent fires or successfully extinguish them before significant damage to life and property occurs.

Passive and Active Fire Protection

Active Fire Protection (AFP) and Passive Fire Protection (PFP) are two sides of the same coin in the realm of fire safety and both are essential for high rise fire safety.

AFP involves systems that actively detect and combat fires, such as alarms and sprinklers.

PFP comprises elements built into the structure of a building to contain and slow the spread of fire and smoke.

Together, they form a comprehensive approach to fire safety, each complementing the other to enhance the overall effectiveness of fire protection strategies.

Passive Fire Protection Measures

This smoke and fire spread can be slowed down by passive fire protection measures such as:

Compartmentalization:

In high-rise buildings, the risk of rapid fire and smoke spread is significantly increased due to the vertical nature of their architecture. Stairwells and elevator shafts can facilitate the upward movement of fire and smoke. Even if a fire is contained to the lower floors, significant upward smoke travel can cause fatalities on upper levels due to toxic fumes and smoke inhalation.

To prevent the spread of fire and smoke, high-rise buildings are constructed with compartmentalization. This involves dividing the high-rise into smaller compartments, each with its own fire-resistant barriers to contain the spread of fire and smoke within a limited area. This prevents the spread of fire, giving occupants more time to evacuate safely and reducing fatalities and property damage. The compartmentalization of smoke is equally important, as it slows down the release of toxic gases and smoke to the rest of the building.

Fire Service Access Elevators:

IBC 403.6.1 mandates an additional fire service elevator for use by the fire service during fires, for buildings with occupied levels above 120 feet. These allow the fire service to quickly access fire floors and also evacuate occupants.

Fire-Resistance-Rated Construction:

• Using non-combustible materials like concrete, steel, and fire-resistant glass for structural elements.
• Including fire-rated doors and fire-resistant insulation in the building to minimize fire spread.
• Using nonflammable cladding. In recent years, flammable cladding used on the exterior walls of buildings has contributed to devastating fires. The Grenfell Tower fire in 2017 resulted in 72 deaths and tragically demonstrated how flammable cladding can facilitate the rapid spread of fire between floors. Had this cladding not been used, it is likely the fire would have been contained to a smaller area when the fire service first responded to the event.

Active Fire Protection Measures

Active fire protection measures are also very important for keeping high rise buildings and its occupants safe. Fire protection engineers can design these measures to fit the unique needs of each different high-rise building.

Active fire protection measures include:

Standpipe Systems

One important fire protection feature found in most high-rise buildings is a standpipe system. Standpipe systems are fixed piping systems that transport water from a reliable water supply to designated areas of the building. This means that water can be directed to the upper levels of the high-rise without the need for overly long and unwieldy hose lays. Hose connections are located at various points throughout the building, allowing firefighters to connect their hoses, access the water supply, and extinguish the fire.

Sprinkler Systems

In high-rise buildings, sprinklers offer critical protection in the event of a fire. In most systems, an automatic sprinkler is activated when the temperature reaches fire levels, usually within the range of 135-165 degrees Fahrenheit. This helps to contain the fire and allow building occupants more time to evacuate safely. The sprinkler activation is limited only to the sprinkler heads near the fire, so unnecessary water damage and disruption do not affect non-fire floors.

Fire Pumps

Fire pumps are frequently used in high-rise buildings. They are used to increase the pressure of a water source to meet the requirements of the suppression systems such as standpipes and sprinklers. To determine if a high-rise building needs a fire pump, hydraulic calculations are performed to determine if the existing water supply can provide sufficient pressure. Adequate water pressure is essential for the reliability and efficiency of fire suppression systems. If the pressure is not high enough, then sprinklers and standpipes might not deliver sufficient water to combat and suppress a fire. Typically, buildings over 75 feet tall require a fire pump to ensure adequate water pressure to the higher floors. This is because as the building height increases, gravity causes a reduction in water pressure, making it more difficult to deliver sufficient pressure to the higher floors.

EVAC Systems

Fire Alarm Systems can be simple or complex, depending on the demands of the specific building. A fire alarm system for a small one-story building will not have the same complexity as a large multi-use high-rise structure that contains different types of occupants.

In high rise buildings an emergency voice/alarm communication system (EVAC) is often incorporated into the fire protection system design. With EVAC systems, their purpose is to provide a clear message that can be heard and understood by occupants. Rather than the horns and strobes associated with traditional fire alarms, these systems communicate clear and audible voice messages. EVAC systems allow for specific instructions that relate to the type of emergency and specific floor.

There are different evacuation strategies used to evacuate building occupants in the instance of a fire.  

Two examples include:

• Simultaneous Evacuation: All occupants on all floors leave at the same time upon alarm signal or notification.
• Phased Evacuation: Only evacuating those people in the immediate vicinity of the fire. This typically involves evacuating the fire floor, the floor above, and the floor below.

The large occupant load and vertical nature of high-rise buildings mean that a phased evacuation approach might be used in a fire instead of a simultaneous evacuation to prevent stairwell congestion.

For example, if a fire broke out in a 30-floor building, the EVAC system would convey a voice message to direct floors 13, 14, and 15 to evacuate and direct them to the nearest exit. Occupants on the other floors may not be notified because they are not in immediate danger, which allows those closest to the fire to evacuate safely through stairwells that are not congested.

RAN Fire Protection Engineers can design solutions to keep your high rise building and its occupants safe. Take a look at our high-rise page for examples of our work.