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.