Fire-resistance rating requirements for smoke control fans and ducts in hotels

Fire-resistance rating requirements for smoke control fans and ducts in hotels

I am fire protection expert Alexander Li. As hotels are assembly occupancies, the fire resistance rating requirements for smoke control and exhaust systems directly affect the safe evacuation of occupants and the effectiveness of smoke control during a fire, and are among the core safety indicators in fire protection design. Based on years of engineering experience, I have handled multiple hotel projects involving acceptance rectification cases caused by insufficient fire resistance ratings of ducts, so the standards must be strictly followed.

Detailed Analysis

1. Fire Resistance Rating Requirements for Smoke Control and Exhaust Fans

• According to Articles 3.3.5 and 4.4.5 of GB 51251-2017, smoke exhaust fans shall be installed in dedicated machine rooms, and the machine rooms shall be separated from other areas by partitions with a fire resistance rating of not less than 2.00h and floor slabs with a fire resistance rating of not less than 1.50h. There is no direct fire resistance rating requirement for the fan itself, but fire dampers installed on ducts must meet the corresponding fire resistance class.
• In an actual project, I participated in the renovation of a five-star hotel where the original design had smoke exhaust fans installed in the open on the roof without a machine room. Subsequently, in accordance with the standard, lightweight fire-resistant partitions with a fire resistance rating of 2.00h were added as enclosure, together with Class A fire doors, and the project passed acceptance.
• Note: If fans are installed outdoors, rain protection and corrosion protection must be considered, and there shall be no combustibles in the surrounding area.

• According to Articles 3.3.8 and 4.4.8 of GB 51251-2017:
• Where smoke exhaust ducts penetrate fire compartments, machine rooms, or important rooms (such as kitchens and transformer/distribution rooms), their fire resistance rating shall not be less than 1.00h.
• For horizontally installed smoke exhaust ducts, if located within a ceiling and the ceiling material is flame-retardant or non-combustible, the fire resistance rating may be reduced to 0.50h, but fire-resistant wrapping shall be used.
• The fire resistance rating requirements for supply air ducts (pressurization air supply) are similar, but generally not less than 0.50h (Article 9.3.13 of GB 50016).
• Case: In an economy hotel project, the design used galvanized sheet steel ducts (thickness 1.2mm) without fire protection treatment where they penetrated fire compartments. The project was judged non-compliant during fire acceptance. Subsequently, 50mm-thick rock wool board wrapping (with galvanized sheet steel outer cladding) was used to achieve a fire resistance rating of 1.00h, and 280℃ fire dampers were added, after which it passed review.
• Material selection: Commonly used fire-resistant wrapping materials include rock wool, aluminum silicate fiber felt, or fire-resistant boards. During construction, it is necessary to ensure tight joints and secure fixing.

• In high-temperature areas such as hotel kitchens and laundries, smoke exhaust ducts shall use steel plates with a thickness of ≥1.5mm, and the fire resistance rating shall not be less than 1.50h (Article 6.2.9 of GB 50016).
• The fire resistance rating of vertical ducts (such as those in shafts) shall not be less than 1.00h, and the shaft walls shall be of non-combustible materials.

Concluding Summary