What does a smoke / fire emergency fan actually have to do, and how is it rated?
It clears hot smoke and combustion gas from a protected space on fire mode — a stairwell, corridor, protected lobby, atrium, car park or tunnel — so the route stays visible and tenable long enough to evacuate. The rating that matters is not flow alone but a temperature-time class: the fan must deliver its full duty at a rated gas temperature for a rated hold time. A common design point is the 300 °C for 2 h class, with higher classes to 400 °C and, at the ceiling of our envelope, 600 °C. We build and test the whole assembly to the class you specify.
How do you keep the motor and bearings alive at the class temperature?
The drive is the part that decides whether the fan finishes the run, so we get it out of the hot gas wherever the layout allows, with an out-of-airstream drive arrangement so the motor never sees the smoke. We fit a shaft cooling disc, also called a heat slinger, to pull heat off the shaft before it reaches the bearing, standard above 400 °C and available from 350 °C. Bearings are heat-rated with high-temperature grease. Where the installation forces the motor into the stream, we specify a motor rated and tested to the same temperature-time class as the fan.
The fan sits idle for years. How do you make sure it starts when it is finally needed?
That is the real risk with an emergency fan, and it is rational to worry about it. We balance to ISO 21940 G6.3, tighter on application, so a long standstill does not set up vibration, and we select bearings and seals for extended idle followed by an instant start, cold or hot. Just as important, we build the fan so it can be test-run and inspected on a schedule, with inspection doors and access designed in. Readiness should be proven periodically, not assumed on the day of a fire.
Can one fan handle both everyday ventilation and fire-mode smoke extract?
Yes, and it is common in car parks and basements. On normal mode the fan runs a CO and NO2 dilution duty, often at reduced speed on a VFD; on fire mode it steps up to full flow at the rated class temperature. We size the fan so both duty points sit on a stable part of the curve, rate the whole assembly to the fire-mode class, and add acoustic scope for the daily ventilation duty near occupied space. Where the two duties are very different, a dedicated fire fan alongside the day-ventilation fans can be the cleaner answer, and we will say so.
How do you handle the fan expanding as the gas heats from ambient to the class temperature?
Going from ambient to 300 or 400 °C in minutes, the shaft grows, the casing expands and the impeller-to-inlet-cone clearance shifts. We size the shaft for that thermal growth and set the running clearance for the hot condition, not the cold one. Expansion joints or flexible connections at inlet and outlet let the casing grow without loading the ducting, and the supports and holding-down are arranged to absorb the movement so the fan keeps turning freely through the temperature ramp.
Do you size the fan at ambient air or at the hot smoke condition?
At the hot condition. Hot smoke is much less dense than ambient air, so a fan sized only at ambient density will fall short of the required flow once the gas is at temperature. We engineer the operating point at the gas density of the temperature-time class, onto the stable region of the selected wheel, so the fan delivers rated flow when the smoke is actually hot. We then verify the curve on our 200 HP VFD test rig before dispatch, at the test condition that represents your duty.
What is the lead time for a smoke / fire emergency fan?
A standard engineered smoke-extract fan runs roughly 10 to 15 weeks order-to-dispatch: offer in 3 to 5 working days, GA drawing 2 to 3 weeks from PO, then manufacture, balance and paint, with performance test and FAT taking about a week. A higher class with an out-of-airstream heat-rated drive package and full thermal scope adds file preparation and runs a little longer. Tell us the class, the drive arrangement and the site constraints and we commit a dated schedule, not a placeholder.
Are your smoke fans certified for the temperature-time class, and to CE and ATEX?
To be precise about the claim: we design, build and performance-test the whole assembly to the stated temperature-time class in-house, and our performance is tested to the AMCA 210 / ISO 5801 method on our 200 HP VFD test rig — that is testing to the method, not an AMCA certification, and we are not an AMCA member. Where a project needs third-party fire-rating certification to a specific national or EN standard, we scope that with a Notified Body and state it explicitly; it is not something we self-award. CE is self-declared per the relevant EU directives and ATEX Zone 2/22 is self-declared per 2014/34/EU, Category 3, where the area classification calls for it. Those are self-declarations of conformity, not third-party certifications. Our only third-party certification is ISO 9001:2015.
