Key Design Points for Mechanical Pressurization Air Supply Systems in Hotel Smoke-Proof Stairwells and Vestibules

Key Design Points for Mechanical Pressurization Air Supply Systems in Hotel Smoke-Proof Stairwells and Vestibules

I am fire protection expert Alexander Li. The mechanical pressurization air supply system for smoke-proof stairwells and their vestibules is the lifeline of fire protection design in high-rise hotel buildings—these areas are the only safe routes for occupant evacuation during a fire, and the success or failure of their design directly determines whether occupants can evacuate safely before being overcome by smoke. In hotel projects, I have seen cases where uneven air volume distribution caused pressure imbalance the moment a vestibule door was opened, and I have also dealt with lessons where systems had to be retrofitted because refuge floors were not considered. Therefore, this design must strictly follow the Technical Standard for Smoke Control and Exhaust Systems in Buildings (GB 51251-2017) and the Code for Fire Protection Design of Buildings (GB 50016-2014, 2018 edition), and be integrated with the actual operating conditions of the hotel.

Design Key Points Analysis

1. System Configuration and Pressure Control

• According to Article 3.1.5 of GB 51251-2017, smoke-proof stairwells and their vestibules should be provided with separate independent mechanical pressurization systems, unless the building height is less than 50m and the stairwell and vestibule share a shaft (subject to calculation verification). Hotels typically have higher floor heights and complex evacuation routes, so I recommend prioritizing independent systems to avoid mutual interference.
• Pressure values must meet: stairwell residual pressure 40-50Pa, vestibule 25-30Pa (Article 3.4.4 of GB 51251-2017). In hotel projects, I once encountered a case where air leakage from the shaft caused insufficient residual pressure in the vestibule—during acceptance testing at a five-star hotel, the residual pressure with vestibule doors closed was only 18Pa, and compliance was achieved only after adding sealing tape to air ducts and adjusting the outlet area.
• Actual Case: In a Shanghai hotel project, the refuge floor was not considered during design (GB 50016 requires hotels with a height greater than 54m to have refuge floors, but this building was 51m and had none), resulting in no reserved outlets for the refuge floor in the stairwell pressurization system. During later retrofit, we added normally closed motorized outlets on the refuge floor, interlocked with the fire alarm, resolving the smoke intrusion problem.

• Air volume shall be calculated according to the formula in Article 3.4.5 of GB 51251-2017: \( L = A_v \cdot v \cdot n \), where \( A_v \) is the door opening area (standard door 2.0m×0.8m), \( v \) is the door opening air velocity (stairwell ≥0.75m/s, vestibule ≥1.0m/s), and \( n \) is the number of simultaneously open doors (typically 2-3 for hotels due to high occupant density). In a 2019 Shenzhen hotel project, we calculated based on 3 doors, resulting in a final air volume of 24,000m³/h, 20% higher than conventional design, but ensuring stable pressure during peak evacuation.
• Outlet layout: one outlet every 2-3 floors in the stairwell (Article 3.3.6 of GB 51251-2017), and one outlet per floor in the vestibule. Outlets should be located above the door opening or on the side wall, avoiding direct blowing onto faces. I once saw a hotel vestibule outlet installed behind the door, causing airflow short-circuiting when the door was opened—it was later relocated to 0.3m above the door, with significant improvement.

• According to Article 4.5.1 of GB 50116-2013 Code for Design of Automatic Fire Alarm Systems, pressurization fans should be started manually or automatically after fire alarm. Hotels often adopt interlocked control: smoke detector alarm → fire control panel → start fan and open vestibule outlets in the corresponding fire compartment.
• Key valves: stairwell outlets normally open, vestibule outlets normally closed (opened on the fire floor and adjacent floors during fire). However, Article 3.3.7 of GB 51251-2017 permits normally open vestibule outlets (with motorized regulating valves required). In operations, I recommend hotels adopt the normally closed scheme, because normally open outlets are prone to being mistakenly closed by guests or accumulating dust, affecting air pressure. For example, a Hangzhou hotel once failed testing because normally open outlets were closed by cleaning staff—the problem was resolved after switching to normally closed motorized outlets.

Engineering Experience and Precautions

• Shaft Airtightness: Hotel building shafts often run through guest room areas; during construction, attention must be paid to plastering and sealing the inner walls of shafts to avoid air leakage. I once used smoke testing to find a 15% air leakage rate in a project's shaft, which only met standards after applying fire-resistant sealant.
• Noise Control: Pressurization fans are usually located in rooftop plant rooms, but noise may be transmitted to guest rooms through air ducts. It is recommended to install silencers at fan outlets and select low-noise fans (noise ≤85dB). A hotel that failed to consider this received continuous guest complaints—the balance between air volume and noise was achieved only after adding silencers and reducing fan speed by 10%.
• Maintenance and Inspection: During hotel operations, fan start/stop and outlet operation need to be tested quarterly. It is recommended to provide access openings at the bottom of shafts for easy cleaning of accumulated dust. I once dealt with a shutdown accident caused by rusted fan bearings—the root cause was failure to lubricate regularly.

Summary