WHAT IS A STAIRWELL PRESSURIZATION SYSTEM?
A stairwell pressurization system is a mechanical smoke control system designed to prevent smoke generated during a fire from entering escape stairwells. The system supplies controlled fresh air to the stair shaft, creates positive pressure, and prevents smoke spreading from the fire area from leaking into the stairwell. Keeping stairwells free of smoke is vital to ensure safe evacuation during a fire. For this reason, stairwell pressurization systems are widely used in high-rise buildings, residences, hotels, hospitals, shopping malls, business centers, public buildings, and industrial facilities.
Stairwell pressurization systems generally operate in integration with fire detection systems, fire alarm systems, building management systems (BMS), smoke control systems, and fire scenarios. When a fire is detected, the system is automatically activated and creates a safe evacuation corridor in the escape stairwells. Today, these systems are regarded as one of the most important active protection solutions in fire safety engineering.
PURPOSE OF STAIRWELL PRESSURIZATION SYSTEMS
The main purpose of stairwell pressurization systems is to ensure that occupants can evacuate the building safely during a fire. The majority of fatalities that occur in fires are caused not by flames, but by smoke and toxic gases. Carbon monoxide (CO), carbon dioxide (CO₂), hydrogen cyanide (HCN), and other toxic gases can reach lethal levels within a very short time.
Stairwell pressurization systems prevent smoke from entering the stairwell by creating positive pressure in escape routes. In this way, building occupants have a longer safe evacuation period. At the same time, the system facilitates the entry of firefighting teams into the building and supports fire intervention operations. Therefore, stairwell pressurization systems are one of the fundamental components of modern fire safety projects, together with sprinkler systems, fire hose cabinets, and smoke exhaust systems.
HOW DOES A STAIRWELL PRESSURIZATION SYSTEM OPERATE?
When the fire alarm is activated, the pressurization fans start automatically. Fresh air taken from the outdoor environment is delivered to the stair shaft through fire-resistant air ducts. As a result of this process, a positive pressure difference is created between the stairwell and the corridor or fire area.
Due to the positive pressure, air movement continuously occurs from the stairwell toward the fire area. Thus, smoke infiltration into the stairwell is prevented. For the system to operate correctly, air leakage, door openings, shaft structure, building height, differential pressure values, and door opening forces must be taken into consideration. In modern systems, differential pressure sensors and variable frequency drives are used to keep pressure values continuously under control.
PRESSURIZATION FAN
The pressurization fan is the most important equipment of the stairwell pressurization system. Fans create the required positive pressure by delivering fresh air taken from the outdoor environment into the stairwell. In fan selection, airflow rate (m³/h), total static pressure (Pa), motor power (kW), energy efficiency, sound level, and fire resistance criteria are taken into consideration.
Fans to be used in fire scenarios are generally selected from certified models with temperature resistance of 300°C/2 hours or 400°C/2 hours. Reliable fan operation is a direct determinant of system performance.
PRESSURE RELIEF DAMPER
Pressure relief dampers are used to control excessive pressure that may occur inside the stairwell. When the pressure inside the stairwell exceeds the specified limits, the damper opens automatically and discharges the excess air.
In this way, smoke control is maintained while door opening forces are kept at acceptable levels. Pressure relief dampers are generally used as motorized or spring-return types and have an important function in terms of system safety.
PRESSURE SENSORS
Pressure sensors continuously measure the differential pressure between the stairwell and adjacent spaces. The data received from the sensors is transmitted to the automation panel, and fan speeds are adjusted instantaneously.
Pressure sensors are of critical importance, especially in high-rise buildings, for controlling pressure variations that may occur due to the stack effect. These devices ensure that the system remains continuously within optimum operating conditions.
VARIABLE FREQUENCY DRIVE (VFD)
A variable frequency drive (VFD) is an electronic drive that provides speed control of fan motors. It automatically increases or decreases the fan speed according to the data received from differential pressure sensors.
In this way, energy savings are achieved and the desired pressure level inside the stairwell is continuously maintained. In systems using VFDs, the fans do not operate continuously at full capacity, which significantly reduces operating costs.
STAIRWELL PRESSURIZATION CALCULATIONS
The design of stairwell pressurization systems is carried out in accordance with the provisions of TS EN 12101-6, EN 12101, NFPA 92, and the Regulation on the Fire Protection of Buildings. The main objective of the design is to prevent smoke passage by creating sufficient differential pressure between the stairwell and the fire area during a fire.
In closed-door scenarios, it is generally targeted to create a differential pressure of approximately 50 Pa. In open-door scenarios, smoke entry into the stairwell is prevented by creating sufficient air velocity through the door opening.
The basic formula used for differential pressure calculation is:
ΔP = P₁ − P₂
Where;
• ΔP = Pressure difference (Pa)
• P₁ = Stairwell internal pressure (Pa)
• P₂ = Corridor or fire area pressure (Pa)
The required airflow rate calculation in the open-door scenario is:
Q = A × V
Where;
• Q = Airflow rate (m³/s)
• A = Door opening area (m²)
• V = Air velocity (m/s)
Air velocities between 0.75 m/s and 2.0 m/s are generally targeted at door openings.
The formula used for calculating door opening force is:
F = ΔP × A
Where;
• F = Force acting on the door (N)
• ΔP = Pressure difference (Pa)
• A = Door area (m²)
In the calculations, air leakage, gaps under doors, shaft leakage, leakage classes of fire doors, duct pressure losses, damper losses, filter resistances, wind loads, and stack effect are also taken into consideration. Especially in high-rise buildings, system performance is verified using CFD (Computational Fluid Dynamics) analyses.
ADVANTAGES OF STAIRWELL PRESSURIZATION SYSTEMS
Stairwell pressurization systems are among the most effective active protection systems in fire safety engineering. These systems prevent dense smoke generated during a fire from reaching escape stairwells and enable building occupants to evacuate safely. Through smoke control, visibility distance is maintained, exposure to toxic gases is reduced, and the panic environment is minimized.
Stairwell pressurization systems also allow firefighting teams to enter the building safely and intervene in the fire. They provide compliance with fire regulations, offer advantages in insurance risk assessments, and increase the overall safety level of the building. Since they can operate in integration with differential pressure sensors, VFD-controlled fans, and building automation systems, they provide energy-efficient, reliable, and long-lasting solutions. They are among the indispensable fire safety systems, especially in high-rise buildings.
APPLICATION AREAS OF STAIRWELL PRESSURIZATION SYSTEMS
Stairwell pressurization systems are widely used in residences, skyscrapers, high-rise office buildings, shopping malls, hospitals, hotels, airports, universities, public buildings, industrial facilities, data centers, laboratories, and logistics centers.
Especially in buildings where the building height increases, smoke control in stairwells becomes much more critical due to the stack effect that occurs during a fire. Within the scope of the Regulation on the Fire Protection of Buildings, stairwell pressurization systems are mandatory in buildings above certain heights. These systems operate together with fire detection systems, sprinkler installations, smoke exhaust systems, and building management systems, forming an important part of the integrated fire safety strategy of the building.
