In short: An FRP fan moves air that would eat a steel fan: acid fumes, chlorine, hydrogen sulfide and wet scrubber exhaust. To select one, you need the airflow and the static pressure the system needs at that flow, plus the gas composition and temperature. The fan's performance curve must cross your system curve at that point, ideally near the fan's best efficiency. Centrifugal FRP fans handle the higher pressures of scrubbers and long duct runs; axial fans suit high flow at low pressure, such as wall and roof exhaust. Resin, motor, drive and any explosion-proof requirement complete the specification. FIBROVX makes FRP fans to order in centrifugal and axial designs, including wall and roof mounted types, sized to your duty.
Where FRP fans are used
Steel and even stainless fans corrode quickly in many process exhausts. FRP fans use a corrosion-resistant resin and glass laminate for the housing and impeller, so the wetted parts do not rust. Typical services:
- Fume scrubber systems, pulling air through a packed-bed scrubber. See our FRP scrubbers guide.
- Chemical and plating shop exhaust, with acid mists and vapors.
- Wastewater odor extraction, with hydrogen sulfide and moist air. See FRP in wastewater treatment plants.
- Laboratory fume hood exhaust, where many chemicals mix.
- Battery rooms, pickling lines and semiconductor exhaust.
Step 1: Define the duty
A fan selection starts with numbers from your system designer:
Airflow. The volume of gas to move, in m³/h or CFM, at actual conditions. For fume extraction, it comes from the hood capture velocity or the number of air changes. For scrubbers, it comes from the scrubber design.
Static pressure. The resistance the fan must overcome at that airflow, in Pa or inches of water gauge. Add up losses from hoods, ducts, elbows, dampers, the scrubber packing and mist eliminator, and the stack. Dirty filters and fouled packing increase resistance over time, so allow a margin.
Gas composition. List every chemical and its concentration, including trace contaminants. This drives the resin choice.
Temperature and humidity. Normal and maximum gas temperature, and whether the gas is saturated (wet scrubber exhaust is). Temperature affects both the resin choice and gas density.
Density and altitude. Fan curves are usually published at standard air density. Hot gas, high altitude and heavy vapors change the density, which changes the pressure the fan develops and the power it draws.
Step 2: Read the fan curve
A fan curve shows, for one fan at one speed, how pressure, power and efficiency change with airflow. The system curve shows how much pressure your system needs at each airflow; it rises roughly with the square of flow. The fan runs where the two curves cross.
Good selection practice:
- Pick a fan whose operating point is near its best efficiency point. That is where it runs quietest, coolest and with the least power.
- Avoid the unstable region on the left of some centrifugal fan curves, where pressure dips. Operating there causes surging and noise.
- Check the power at the operating point and at maximum flow, so the motor is not overloaded if the system resistance falls (for example, with a damper open or a filter removed).
Ask for curves tested to a recognized method. Many fan makers rate their products using laboratory test methods published by AMCA (the Air Movement and Control Association). FIBROVX provides the performance data for the fan quoted.
Step 3: The fan laws
For the same fan and gas density, the fan affinity laws describe what happens when you change speed:
- Airflow changes in proportion to speed.
- Pressure changes with the square of speed.
- Power changes with the cube of speed.
So a 10% speed increase gives about 10% more airflow, 21% more pressure and 33% more power. This is why a variable-frequency drive (VFD) is useful: it lets you trim the fan to the actual system and save energy. It also shows why oversizing is costly. The laws are approximations; use the fan maker's data for final figures.
Step 4: Centrifugal or axial?
| Centrifugal FRP fan | Axial FRP fan | |
|---|---|---|
| Pressure | Medium to high | Low |
| Typical use | Scrubbers, ducted fume systems, long runs | Wall and roof exhaust, general ventilation |
| Airflow | Low to high | High |
| Footprint | Larger, with scroll housing | Compact, in line with the duct or wall |
| Noise | Generally lower at the same duty | Can be higher at high tip speeds |
Most ducted fume systems with a scrubber need a centrifugal fan because packed beds and mist eliminators add significant pressure drop. Axial fans and roof or wall units suit spaces that need plenty of air changes with little ductwork.
Other choices to make:
- Drive: direct drive (motor on the shaft) is compact and low-maintenance. Belt drive lets you change speed with pulleys and keeps the motor out of the hot gas path.
- Arrangement and discharge direction: to fit your duct layout.
- Inlet and outlet connections: flanged to match your ducts.
- Drain: a housing drain lets condensate escape from wet exhaust.
- Inspection door: for impeller checks and cleaning.
- Shaft seal: to limit leakage of corrosive gas along the shaft.
Step 5: Resin and temperature
The resin system decides chemical resistance and temperature limits. Vinyl ester resins are widely used for corrosive fume fans; other resins can be chosen for specific chemicals. Give us the full gas composition and maximum temperature, and we will propose the laminate. Our FRP chemical resistance guide and resin comparison explain the options.
Step 6: Motors, hazardous areas and static
If the exhaust can contain flammable vapors, the fan system must be designed for that hazard. In the US, NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Particulate Solids, sets requirements for such exhaust systems, and your hazardous area classification sets the motor requirement.
Points to consider:
- Explosion-proof motors may be needed for the area classification. Tell us the zone or class and your local certification requirement.
- Static electricity. FRP is an insulator, so static charge can build up in some services. Where flammable vapors are possible, ask about conductive laminates and grounding of the fan.
- Spark resistance. AMCA publishes spark-resistant construction classifications for fans. If your specification calls for one, tell us at the start.
FIBROVX supplies motors to match the voltage and frequency of your country. We confirm motor type, protection and any certification for the item quoted in writing, and we do not claim certifications we do not hold.
Step 7: Noise and vibration
- Select near the best efficiency point to keep noise down.
- Use flexible connectors at the inlet and outlet so vibration is not passed to the ducts.
- Mount the fan on a rigid base, with vibration isolators where needed.
- Balance the impeller and check vibration at start-up and during service.
- Consider silencers on the discharge or stack if the site has noise limits.
Maintenance
- Inspect the impeller for buildup, erosion and cracks. Buildup causes imbalance and vibration.
- Check drains so condensate does not collect in the housing.
- Check bearings and belts on the schedule in the manual.
- Watch vibration levels; rising vibration often means buildup or bearing wear.
- Check the shaft seal for leaks.
What to send for a quote
FIBROVX makes FRP fans to order. Please send:
- Airflow and static pressure at the design point.
- Gas composition and temperature (normal and maximum), and humidity.
- Fan type and mounting: centrifugal or axial, wall, roof or floor mounted, discharge direction.
- Motor voltage and frequency for your country.
- Explosion-proof requirement and area classification, if any.
- Noise limits, if any, and drive preference.
Fans are often supplied with FRP acid fume scrubbers or bio-deodorization units. Browse the Air Pollution & Odor Control collection, or read the packed-bed scrubber sizing guide.
Need a quote or a drawing check?
FIBROVX manufactures FRP products in our own factory in China and builds every item to order: sizes, resin system, color, molds and OEM branding. Send your application, dimensions or drawing, quantity and destination port.
Request a QuoteCommon mistakes
- Guessing the static pressure. Add up every loss, plus a margin for fouling.
- Ignoring gas density. Hot gas and altitude change fan performance.
- Selecting far from best efficiency. More noise, more power, shorter life.
- No drain on a wet exhaust fan. Condensate collects and unbalances the impeller.
- Forgetting flammable vapors. Check NFPA 91, area classification and static control.
Key terms
- Static pressure: The resistance the fan must overcome to move air through the system.
- Fan curve: A chart of a fan's pressure, power and efficiency against airflow.
- System curve: A chart of the pressure a duct system needs at each airflow.
- Best efficiency point: The airflow at which the fan runs most efficiently.
Fans in a treatment system
Fans often push gas through an RTO or scrubber to an FRP stack; connections use FRP fittings and flanges.
Watch: FRP Fans in Systems in 27 Seconds
FAQ
Why use an FRP fan instead of stainless steel? Many acid and chlorine fumes attack stainless steel. FRP with a suitable resin resists them.
Centrifugal or axial for a scrubber? Usually centrifugal, because scrubbers add significant pressure drop.
Can FRP fans handle hot gas? Within the resin's temperature limit. Tell us the maximum gas temperature.
Do you supply explosion-proof motors? Tell us your area classification and certification requirement, and we will confirm what we can supply for the fan quoted.
Can the fan match my existing ducts? Yes. Inlet and outlet sizes, discharge direction and mounting are customized.
Related guides
- FRP Scrubbers Guide
- Packed-Bed Scrubber Sizing
- Biofilter vs Chemical Scrubber
- FRP Chemical Resistance Guide
- Industries we serve
Sources
- NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Particulate Solids (2026 edition): https://www.nfpa.org/codes-and-standards/nfpa-91-standard-development/91
- AMCA, Air Movement and Control Association International (fan test and spark-resistance standards): https://www.amca.org/
- The Engineering ToolBox, Fan affinity laws: https://www.engineeringtoolbox.com/fan-affinity-laws-d_196.html