Comparison Between UL 555/UL 555S (U.S. Standard) and GB 15930/GB/T 17428 (Chinese Standard)

UL 555 and UL 555S are U.S. standards for fire dampers and smoke dampers, while GB 15930 and GB/T 17428 are the corresponding Chinese standards. The main differences lie in testing methods, classification, performance requirements, and application scenarios.

1. Applicable Standards

Standard	Scope	Classification
UL 555	Fire Dampers	Classified by fire resistance rating (1.5 hours, 3 hours)
UL 555S	Smoke Dampers	Classified by smoke leakage rating (Class I, II, III)
GB 15930-2007	Fire Dampers & Fire-Smoke Dampers	Classified by closing mechanism and temperature activation (70°C, 280°C)
GB/T 17428-2019	Smoke Dampers	Classified by air leakage level (A, B, C)

2. Key Technical Differences

Comparison Item	UL 555 (Fire Dampers)	GB 15930 (Fire Dampers)
Fire Resistance	1.5 hours or 3 hours	1.0 hour or 1.5 hours
Dynamic Closure Test	Required, typically tested at 2000-4000 fpm airflow	Required, tested at 15 m/s airflow
Installation Method	Allows rigid duct connection	Requires sealed installation with ducts
Automatic Closure Mechanism	Mechanical (165°F（74°C）or 212°F（100°C)) or electrically actuated	Thermal fuse release (70°C/280°C) or electrical closure
Duct Pressure Rating	Designed for both positive and negative pressure ducts	Mainly used in smoke exhaust or ventilation ducts

Comparison Item	UL 555S (Smoke Dampers)	GB/T 17428 (Smoke Dampers)
Smoke Leakage Classification	Class I: ≤8 cfm/sq.ft	A Level: ≤200 m³/(㎡·h)
Operating Temperature	250°F (121°C) or 350°F (177°C)	280°C, 250°C, 150°C
Closure Under Airflow	Tested at airflow speeds of 2000-4000 fpm	Tested at 15 m/s
Actuation & Cycling Test	20,000 open-close cycles	1,000 cycles (for electrically controlled dampers)
Remote Control	Electric or pneumatic actuator required	Mainly electric control, less pneumatic control

3. Major Differences Summary

(1) Fire Resistance Performance

• UL 555 requires fire dampers to maintain structural integrity for 1.5 or 3 hours, whereas GB 15930 requires only 1.0 or 1.5 hours.
• UL 555 fire testing follows UL 263, simulating real-world fire conditions inside duct systems, while GB 15930 uses a national fire testing furnace.

(2) Smoke Leakage Classification

• UL 555S has Class I, II, III ratings, with Class I allowing a maximum leakage of 8 cfm (~13.6 m³/h) per square foot.
• GB/T 17428 has A, B, C levels, with the strictest level A allowing ≤200 m³/(㎡·h), which is a more lenient requirement compared to UL.

(3) Automatic Closure Mechanism

• UL 555/555S primarily use electric or mechanical actuators for automatic closure and can reset multiple times.
• GB 15930 relies on a thermal fuse (70°C or 280°C) for closure, which is usually a one-time activation mechanism.

(4) Airflow Speed Testing

• UL 555S requires dampers to close at airflow speeds of 2000-4000 fpm (10-20 m/s) to ensure functionality in HVAC systems.
• GB 15930 tests dampers at 15 m/s, with no strict requirement for higher airflow speeds.

(5) Product Lifespan Requirements

• UL 555S mandates a durability test with 20,000 open-close cycles, ensuring long-term reliability.
• GB/T 17428 only requires 1,000 cycles, meaning the product is not expected to last as long in repeated operations.

4. Summary Table

Comparison Item	UL 555/555S (U.S. Standard)	GB 15930/GB/T 17428 (Chinese Standard)
Fire Resistance	1.5 or 3 hours	1.0 or 1.5 hours
Smoke Leakage Level	Class I: ≤8 cfm/sq.ft	A Level: ≤200 m³/(㎡·h)
Closure Mechanism	Electric or mechanical	Thermal fuse (70°C/280°C)
Airflow Speed Testing	2000-4000 fpm (10-20 m/s)	15 m/s
Cycling Durability	20,000 cycles	1,000 cycles

Key Takeaways:

✅ UL 555/555S focuses on stricter fire resistance, airflow adaptation, and automation, making it more suitable for complex HVAC systems.
✅ GB 15930/GB/T 17428 focuses on smoke/fire prevention in exhaust ducts, with looser leakage and durability requirements.
✅ For export to UL markets, manufacturers must enhance high-temperature endurance, airtightness, and remote control capabilities.