Design of a fire escape air compressor system (Stair Pressurization System)

Its main purpose is to prevent smoke from entering the fire escape hall during a fire.

By using compressed air to have a higher pressure than other areas. so that smoke cannot spread in

✅ Guidelines for calculating and designing a compressed air system for fire escapes (according to standards / / YLF)

1. Set the differential pressure value (Pressure Differential).

Situation Recommended pressure value
No air leaks (Static) 12.5 – 50 Pa
There is a door opening (Dynamic) ≥ 12.5 Pa where the door is open.
According to the Ministry of Culture, not more than 60 Pa (to open the door)

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2. Find the amount of air that must be paid (Airflow Rate).

2.1 Static type (no air leaks)

Used in cases where compressed air is used to maintain pressure when there is no door open, such as:

Q = V x A

 • Q = Air volume (m³/s)
 • V = Air velocity at the air outlet (2 – 5 m/s).
 • A = Air outlet area (m²)

2.2 Dynamic type (with opening door)

It takes enough air to maintain the pressure even when the door is open. By calculating the air leaking through the door gap.

Formula:

Q = C × A × √(2 × ΔP / ρ)

 • Q = Air flow rate (m³/s)
 • C = Discharge coefficient (approximately 0.61)
 • A = Door opening area. (The space between the top and bottom margins is combined)
 • ΔP = pressure difference (Pa)
 • ρ = density of air (~1.2 kg/m³)

If there is no specification value Assume total door space 2 cm x width 0.9 m = 0.018 m²

3. Specifies the number of doors that may be opened simultaneously.
 • Normal worst case calculation: The door on the fire floor is 1 open.
 • If you want to allow for the opening of two doors 2 at the same time, you must multiply the leakage value 2 times.

4. Consider the height of the building.

Because hot air rises Fans may need to be installed in several vertical locations to maintain consistent pressure, such as:
 • Building < 10 Floor: 1 Fan enough
 • Building > 20 floor: There should be an air supply point on every 5 floor or use a Duct Vertical Shaft.

5. Calculate fan and duct size.
Use the Q information obtained from item 2 to determine the fan size and air duct size and calculate the pressure drop (Pressure Loss) so that the fan can supply the desired amount of air.

6. Power backup system (Emergency Power)
The compressed air fan system must be connected to emergency power supply
And it should have a separate control system from the normal HVAC system.

7. Control and command system
 • Controlled with Fire Alarm System to allow the fan to run automatically in the event of a fire.
 • Control the pressure with a Pressure Sensor + Variable Speed Fan (VFD) to maintain the pressure at the desired value.

Summary of Design Check List
 • Set the desired pressure value (12.5 – 50 Pa).
 • Calculate Q based on leaky channels and open doors.
 • Select the fan to achieve CFM or m³/hr according to Q.
 • Consider air ducts according to building height.
 • Use backup power + automatic operation system.