Smoke exhaust system design requirements for hotel atriums and lobbies
I am fire protection expert Alexander Li. The smoke exhaust system design for hotel atriums and lobbies is one of the core challenges in fire protection engineering, directly affecting the safety of occupant evacuation and the effectiveness of smoke control during a fire. As a large-volume space, an atrium with improper smoke exhaust design may allow smoke to spread rapidly to upper-level corridors or guest room areas, causing evacuation routes to fail. The following is a detailed analysis based on codes and practice.
Core Design Requirements
According to Article 4.3.2 of the 《Technical Standard for Smoke Control and Exhaust Systems in Buildings》(GB 51251-2017), natural smoke exhaust should be prioritized for atrium smoke exhaust systems, but the opening area must be no less than 5% of the floor area. In actual projects, hotel lobbies often cannot meet natural smoke exhaust conditions due to limitations of glass curtain walls or skylights, so mechanical smoke exhaust systems are mostly adopted. The mechanical smoke exhaust rate is calculated according to Article 4.6.5 of GB 51251-2017: the atrium smoke exhaust rate is determined by the clear height of the building space. When the clear height is greater than 6 m, the smoke exhaust rate is calculated at 60 m³/h per square meter (and shall not be less than 90,000 m³/h); if the clear height is less than or equal to 6 m, it is calculated at 60 m³/h per square meter, but the air change rate shall be no less than 6 times/h. For example, for an atrium with a clear height of 15 m and an area of 500 ㎡, the smoke exhaust rate needs to reach 500×60=30,000 m³/h, but the code lower limit is 90,000 m³/h, so the actual design value is taken as 90,000 m³/h.
Key Points of System Design
1. Zoning and Airflow Organization: Atriums are often connected to adjacent areas (such as lobby bars and reception), and smoke control zones need to be divided by smoke curtains or fire shutters. The height of smoke curtains shall not be less than 0.5 m and shall be lower than the bottom of the smoke reservoir (the smoke reservoir height is calculated according to Article 4.6.2 of GB 51251-2017, usually 10% of the clear space height). For example, in the atrium of a five-star hotel lobby with a clear height of 12 m, the smoke reservoir height is taken as 1.2 m, and the smoke curtain is set at the 6 m elevation to ensure that smoke accumulates at the top.
2. Make-up Air System: Make-up air must be provided when the atrium exhausts smoke, and the make-up air volume shall not be less than 50% of the smoke exhaust volume (Article 4.5.2 of GB 51251-2017). A common practice is to use the lobby entrance for natural make-up air or to install mechanical make-up air fans. In one project, because no make-up air was designed, negative pressure formed during smoke exhaust and doors could not be opened; this was solved by adding make-up air inlets.
3. Fans and Ducts: Smoke exhaust fans should be installed at the top of the atrium or on the roof, with a fire resistance rating of not less than 1.5 h (Article 4.4.5 of GB 51251-2017). Duct air velocity should not exceed 20 m/s, and non-combustible materials (galvanized steel sheet or fireproof board) shall be used. Case: When the atrium smoke exhaust duct of a hotel crossed a fire compartment, no 280℃ fire damper was installed, and rectification was ordered during acceptance.
Actual Project Case
In a five-star hotel in a coastal city, the atrium has an area of 800 ㎡ and a clear height of 18 m, and a mechanical smoke exhaust system was adopted in the design. The smoke exhaust rate was taken as 90,000 m³/h according to the code, with 4 smoke exhaust fans (22,500 m³/h each), and make-up air was supplied naturally through louvered openings at the lobby entrance. However, during commissioning it was found that insufficient make-up air caused smoke exhaust efficiency to drop by 40%. Ultimately, 2 make-up air fans (total volume 45,000 m³/h) were added, and CFD simulation was used to optimize airflow organization so that the smoke layer remained stable within the smoke reservoir.
Concluding Summary
The design of hotel atrium smoke exhaust systems must strictly follow GB 51251-2017, with key control of smoke exhaust rate, make-up air balance, and smoke control zone division, and airflow organization should be optimized in combination with actual space conditions. The above are reference opinions. The actual project conditions still need to be further comprehensively evaluated and implemented in combination with specific operating conditions, site conditions, and other factors.