A building fire creates two simultaneous demands: evacuating occupants and maintaining tenable escape routes. Mechanical smoke extraction systems must keep operating while temperatures around the fan rise sharply. A standard ventilation fan is not designed for this duty. A dedicated fire smoke exhaust fan is engineered to survive elevated temperatures for a defined period, and its specification must match the fire engineering strategy of the building.

Understanding Temperature Classes

Fire-rated fans are classified by the temperature they can withstand and the duration they must continue running. SINDFAN fire-rated axial fans are available in three standard classes:

  • 250°C for 1 hour
  • 300°C for 2 hours
  • 400°C for 1 hour

These ratings correspond to the fire scenarios defined in project specifications and fire engineering reports. A system serving a large enclosed space may require a 400°C/1h rating, while another duty may be engineered for 300°C/2h. The required class must be stated clearly by the specifying engineer and verified against the fan manufacturer’s declared rating.

SINDFAN fire-rated axial fans in this range are fitted with jet fan motors, selected for their suitability in continuously operating, high-temperature smoke extraction applications.

Why a Fire Smoke Exhaust Fan Differs from a Standard Fan

During evacuation, the fan must move air even as the airstream temperature climbs toward its rated limit. Three components are critical:

  • Blade material: The impeller must retain its mechanical strength and geometry at operating temperature.
  • Motor insulation: Standard insulation degrades quickly under heat. Fire-rated motors use insulation classes that resist breakdown, preventing winding failure during the rated period.
  • Bearing grease: Ordinary grease liquefies or carbonises at high temperature, causing bearing seizure. Fire-rated fans use high-temperature grease that maintains lubrication through the rated duration.

These differences mean a standard fan cannot simply be re-labelled as fire-rated. The complete rotating assembly must be designed and verified for thermal duty.

Impeller Materials and Their Limits

The impeller is the most heat-exposed component in a smoke extraction fan. Its material must hold shape and strength at the rated temperature because a collapsing blade set will stop the fan and disable the smoke control system.

SINDFAN fire-rated axial fans use cast aluminium LM6 blades. LM6 is a silicon-based aluminium alloy with good elevated-temperature properties and resistance to thermal shock. It is suitable for service up to the 400°C class.

Other materials used in standard fan construction are not safe substitutes:

  • GRP (glass-reinforced plastic) impellers are limited to approximately 70°C ceiling temperature. They soften and lose structural integrity well before fire conditions develop.
  • Nylon66 impellers are limited to approximately 150°C. Above this temperature the polymer degrades, and blades can deform or detach.

Neither GRP nor nylon66 should be considered for a fire smoke exhaust fan, regardless of the fan’s catalogue description. If the project specifies a 250°C or higher rating, verify the impeller material before installation.

Testing and Balancing

Performance claims for fire-rated fans must be supported by test data. SINDFAN fire-rated axial fans are performance-tested to AMCA 210 / ISO 5801, providing a reliable basis for airflow and pressure selection. Rotating assemblies are dynamically balanced to ISO 1940 G4.0, limiting vibration and extending bearing and motor life in continuous duty.

AMCA 210 / ISO 5801 confirms aerodynamic performance, while ISO 1940 G4.0 confirms the mechanical quality of the rotating assembly. Both are required in a properly specified fire-rated fan.

Selecting the Correct Fire Rated Fan 400°C Option

Selection should be based on the building’s fire engineering strategy, including required extraction flow rate, system pressure drop, and the temperature/time curve of the design fire. Once these parameters are known, a suitable fan can be selected and checked against the relevant class.

Confirm the class rating, impeller material, motor design, and supporting test standards with the manufacturer before purchase.

Contact SINDFAN

To discuss a smoke extraction fan requirement, or to confirm the correct fire rated fan 400°C duty for your project, contact SINDFAN on WhatsApp at +852 9524 8434 or email info@sind-tech.com with your duty details: required airflow, pressure, temperature class, and installation arrangement.