An axial fan is a fan that moves air parallel to its rotating shaft, using angled blades to generate high airflow at relatively low pressure. A centrifugal fan is a fan that draws air in along the shaft axis and discharges it radially, at roughly 90 degrees to the intake direction, building significantly higher static pressure in the process. The choice between them comes down to one variable above all others: how much resistance your system creates. As a practical rule of thumb, axial fans usually deliver better value below about 400 Pa of system resistance, while centrifugal fans become the safer choice above roughly 500 Pa.
Key Takeaway
System static pressure determines the right fan type more than any other variable. Axial fans suit open, low-resistance applications below roughly 400 Pa. Centrifugal fans handle ducted, high-resistance systems above 500 Pa. Choosing by airflow alone — without checking static pressure — is the single most common cause of fan under performance in the field.
How Axial and Centrifugal Fans Work
Airflow direction: axial fan (parallel to shaft) vs centrifugal fan (90-degree radial discharge)
How an Axial Fan Moves Air
An axial fan is a device that propels air in a direction parallel to its rotating shaft, using a set of pitched blades mounted on a central hub. As the hub spins, each blade creates a pressure difference between its leading and trailing faces, pushing a continuous column of air forward along the shaft axis. If you want to know more about axial fan, please see what is an axial fan and Axial Fan vs Blower.
This geometry makes axial fans efficient at moving large volumes of air against modest resistance. A single axial unit can deliver airflow from a few hundred m3/h in small cooling tasks to more than 830,000 m3/h in large tunnel or industrial ventilation systems, per published industrial fan performance data. The trade-off is static pressure. Push an axial fan against a system with real resistance: long ductwork, multiple filters, or dense bends. Delivered airflow drops sharply.
We’ve seen this enough times to say: always check static pressure before finalizing any axial fan selection.
How a Centrifugal Fan Moves Air
A centrifugal fan is a machine that draws air through an axial inlet and discharges it radially, converting rotational energy into static pressure through centrifugal force. Air enters the center of the rotating impeller, accelerates outward as the impeller spins, and exits through the scroll casing at roughly 90 degrees to the intake direction. AC centrifugal fans are the most widely used type in commercial HVAC and industrial ducted systems.
This design produces substantially higher static pressure than axial fans can achieve at comparable sizes. Centrifugal fans commonly operate between 500 Pa and several thousand Pa, and heavy-duty industrial designs reach 25,000 Pa or more. That pressure capability is what makes centrifugal fans the standard choice for systems with real resistance: duct runs, filter banks, scrubber towers, and coil assemblies.
But here’s the thing. Higher pressure capability doesn’t make centrifugal fans universally better. In open, low-resistance applications, a centrifugal fan often costs more to buy, more to run, and more to maintain, for no performance advantage over a properly sized axial unit. Here is our centrifugal fan cluster. And if you want to know more about centrifugal fans, see 5 Types of Centrifugal Fans and backward curved centrifugal fan and Forwarder Curved and Backward Curved Centrifugal Fans.
To more about impeller fan design.
Performance Comparison: Axial vs Centrifugal
Axial vs centrifugal fan: key performance metrics compared
| Feature | Axial Fan | Centrifugal Fan |
|---|---|---|
| Airflow direction | Parallel to shaft | 90 degree radial discharge |
| Typical static pressure range | Up to 500-1,000 Pa | 500 Pa to 25,000 Pa+ |
| Peak airflow volume | Very high (up to 830,000 m3/h) | High (up to 500,000 m3/h) |
| Efficiency in low-pressure systems | High | Lower (overspecified for the job) |
| Efficiency in high-pressure systems | Low (performance drops sharply) | High |
| Noise profile | Higher broadband noise at speed | Can be quieter in many ducted installations |
| Physical footprint | Compact, straight-through layout | Larger, requires discharge clearance |
| Initial cost | Lower | Higher |
| Maintenance complexity | Simpler (fewer components) | More involved (impeller, housing, bearings) |
| Contamination tolerance | Moderate | Higher (especially radial-blade designs) |
| Best for | Open ventilation, equipment cooling | Ducted systems, exhaust, dust collection |
Per AMCA Standard 210, fan performance data is rated at controlled test conditions. Real-world delivered airflow depends on actual system resistance, not free-air ratings. A fan that looks adequate on a datasheet may deliver 30 to 50% less airflow once installed in a real system with filters, bends, and ductwork.
The Static Pressure Threshold: Where the Decision Usually Happens
Static pressure thresholds for axial vs centrifugal fan selection — a practical rule of thumb
Static pressure is the resistance that a fan must push air against throughout the system. It comes from duct length, bends, filters, dampers, coils, hoods, and any other restriction in the airflow path.
Most axial vs centrifugal selection mistakes happen because this number is either unknown or underestimated at the start of a project. The DOE’s Improving Fan System Performance guide identifies this as one of the leading sources of energy waste in industrial ventilation: fans selected against incorrect system resistance estimates that leave equipment either underperforming or running at excessive power draw.
As a practical rule of thumb, here is how the decision typically falls:
| System resistance | Typical recommendation |
|---|---|
| Below 100 Pa | Axial fan. Open system, low resistance, axial delivers strong value |
| 100 to 400 Pa | Evaluate carefully. Axial may work with proper sizing and margin; layout matters |
| 400 to 500 Pa | Transition zone. Centrifugal usually makes more sense |
| Above 500 Pa | Centrifugal fan. Axial fans lose both flow and efficiency fast above this range |
| Above 1,000 Pa | Centrifugal or blower. Not an axial application |
The Forward-Curved Fan Trap
Important Note
In non-ducted or near-zero-resistance applications, forward-curved centrifugal fans can overload and burn out their motors. Their rising power curve means power demand can continue rising toward motor overload as airflow increases against no resistance. Do not substitute a forward-curved centrifugal fan for an axial unit in an open, unducted application — even if the airflow numbers look similar on a datasheet.
Axial fans don’t have this problem. Their power curve self-limits in open conditions.
For systems in the 100 to 400 Pa range, our fan static pressure explained guide walks through how to calculate system resistance before committing to a fan family.
Worked Example 1: Where an Axial Fan Fits
Six axial fans, 18,000 m3/h each, cross-ventilating an open-ceiling workshop
Take a precision electronics workshop: a 1,200 square meter production floor with a 6-meter open ceiling and no suspended ductwork.
| Parameter | Value |
|---|---|
| Floor area | 1,200 m2, 6 m open ceiling |
| Internal heat load | 180 kW |
| Peak ambient temperature | 38 deg C |
| System duct resistance | Approximately 120 Pa |
| Target air changes | 8 or more per hour |
| Fan selection | 6 x low-noise axial fans, 18,000 m3/h each, 150 Pa, 1.5 kW |
A layout that fits this profile: six low-noise axial fans, each rated at about 18,000 m3/h and 150 Pa working pressure, mounted at equal intervals along the exterior walls to create cross-ventilation, for about 9 kW of installed power in total.
This profile fits the axial selection logic exactly. Low resistance, open layout, high airflow target, clean ambient air. Nothing in that profile needed centrifugal capability. Choosing axial keeps the project simpler, quieter, and cheaper to run.
Worked Example 2: Where an Axial Fan Fails
Axial fan rated at 320 Pa in an 850 Pa system — the root cause of the paint shop failure
Not every selection gets it right the first time.
Now take a coating-fume exhaust that draws fumes from a paint shop into a scrubber tower before discharge, and suppose a propeller-type axial fan has been installed for it.
| Parameter | Value |
|---|---|
| System | Coating fume exhaust to scrubber tower |
| System components | 6 duct elbows, 3 filter stages, scrubber tower resistance |
| Required exhaust volume | 25,000 m3/h |
| System resistance | Approximately 850 Pa |
| Initial selection (error) | Propeller-type axial fan, rated 24,000 m3/h, 320 Pa |
| Delivered airflow | 16,000 m3/h (36% below target) |
| Scrubber efficiency | 60% (below regulatory threshold) |
| Motor temperature | 90 deg C (over-temperature) |
The axial fan was rated at 24,000 m3/h and 320 Pa. That second number was the problem. The system needed 850 Pa. The fan could only produce 320 Pa. The result was a shortfall that the motor tried to compensate for by drawing excess current, overheating, and failing.
A system like this cannot meet discharge requirements: the motor runs at a fire-risk temperature and fume capture is too weak for the scrubber to work properly.
The fix is a high-pressure centrifugal fan sized to the real system curve, for example a 9-19 type rated around 26,000 m3/h and 950 Pa, installed on a vibration-damped base with a discharge silencer.
| Parameter | Initial axial (error) | Corrected centrifugal |
|---|---|---|
| Airflow | 16,000 m3/h | 25,800 m3/h |
| Motor temperature | 90 deg C | 65 deg C |
| Operating power | 18 kW (overloaded) | 15 kW (rated) |
AMCA’s fan and system curve guidance makes this point clearly: fan selection must be made at the operating point on the system curve, not at free-air performance. API STD 673, which covers centrifugal fans for petroleum, chemical, and gas industry services, reinforces the same principle for exhaust systems handling contaminated or reactive air streams: fan selection must reflect actual system resistance, not catalog airflow ratings.
In industrial thermal and ventilation design, pressure losses across the system are often underestimated at the specification stage, and the resulting fan underperformance is one of the most common and preventable failures in the field. The paint shop example shows exactly that: the system resistance is real, and a fan selection that ignores it fails quickly.
For industrial exhaust applications involving fumes, dust, or process air, see our centrifugal exhaust fan guide for selection criteria specific to those conditions.
Contamination, Noise, and Special Environments
Radial blade vs backward-curved airfoil: contamination tolerance differences
Can Centrifugal Fans Handle Dusty Air?
A centrifugal fan is better suited to contaminated airstreams than an axial fan, but wheel geometry still determines how well it holds up over time. In applications with heavy dust, fibers, sticky particulate, or oil mist, radial-blade centrifugal fans often outperform backward-curved and airfoil designs because their simpler blade geometry resists deposit buildup and allows easier cleaning.
Backward-curved and airfoil impellers deliver higher efficiency in clean air. In dirty air, their complex blade profiles can accumulate deposits unevenly, causing vibration, rotor imbalance, and accelerated bearing wear. ISO 1940-1 covers balance quality requirements for fan rotors in a constant rigid state. Contamination-induced imbalance is one of the primary causes of early bearing failure in industrial exhaust fans.
For light dust in relatively clean exhaust streams, backward-curved centrifugal fans work well. For sticky, fibrous, or heavy particulate, radial-blade designs are the safer long-term choice. See our dust collection fan guide for contamination-specific selection criteria.
Noise Differences in Practice
An axial fan tends to produce more broadband noise than a centrifugal fan at equivalent duty points, mainly because the blades cut directly through the airstream without the acoustic buffering of a scroll casing.
That said, axial fans aren’t unusable in noise-sensitive locations. Blade geometry, tip clearance, operating speed, and mounting all affect the actual noise level. In the electronics plant project above, measured floor noise stayed below 65 dB(A) with proper fan selection and wall-mount positioning.
Centrifugal fans can be quieter in many ducted installations for a structural reason: the scroll casing contains much of the turbulence generated by the impeller. But centrifugal fans spinning at high speed still produce meaningful noise, particularly if the impeller is operating off its design point or if rotor balance has degraded. Here is a comprehensive for noise reduction.
ProTip
If noise is a constraint in your project, start with our axial fan noise reduction solutions guide before defaulting to centrifugal. A well-selected axial fan often meets noise targets at lower total system cost.
High-Temperature and Corrosive Environments
Standard axial and centrifugal fans share the same basic material and motor limits. Above roughly 60 to 80 deg C, both require special configurations: high-temperature motor insulation, heat-rated bearings, and thermal shielding where the motor is exposed to hot air.
Above 200 deg C, material selection becomes the deciding factor. Standard steel casings, aluminum impellers, and off-the-shelf motors are no longer reliable at these temperatures. This is where purpose-built high-temperature configurations enter the specification, regardless of whether axial or centrifugal is the base fan type.
See our high-temperature axial flow fan guide for application-specific guidance on thermal limits and material options.
Within Centrifugal Fans: Forward Curved vs Backward Curved
Forward-curved vs backward-curved impeller: blade geometry and power curve behavior compared
Once centrifugal is the right family, wheel geometry determines efficiency, noise behavior, motor safety, and long-term reliability.
A forward-curved centrifugal fan is a design that uses impeller blades curved in the same direction as rotation, producing high airflow at relatively low rotational speeds. Forward-curved fans are common in HVAC air-handling units and low-to-medium pressure duties. But their rising power curve creates motor overload risk if system resistance drops unexpectedly. That’s the forward-curved trap described earlier in this article.
A backward-curved centrifugal fan is a design that uses impeller blades curved against the direction of rotation, producing a non-overloading power curve and higher peak efficiency than forward-curved equivalents. Per AMCA Standard 210, high-quality backward-curved fans achieve 75 to 85% static efficiency at their design point, compared to 55 to 65% for forward-curved designs. In properly selected backward-curved designs, the power curve is typically non-overloading, which greatly reduces motor overload risk as airflow increases past the peak.
For most industrial exhaust and process air applications above 400 Pa, backward-curved is the safer default. The efficiency difference compounds over the operating life of the system, and the non-overloading curve removes one entire category of failure risk.
For a full side-by-side comparison, see backward-curved vs forward-curved centrifugal fans.
A note on radial fans. Within the centrifugal family, radial-blade designs are sometimes called paddle-wheel fans. They sit at the low-efficiency end of the spectrum, but the high-tolerance end for dirty air. If the airstream carries abrasive particles, sticky fibres, or heavy moisture, radial blades resist deposit buildup better than any curved profile. That’s why you see them in wood dust extraction, grain handling, and aggregate processing. For clean or lightly contaminated air, backward-curved designs give you better efficiency at the same duty point.
Five-Question Decision Checklist
Five-question decision checklist for axial vs centrifugal fan selection
Answer these in order. The pattern that emerges usually points to the right fan family.
- 1 What is the system static pressure? Measure or calculate the total resistance from ducts, filters, bends, dampers, and any other restriction in the airflow path. If this number is unknown, get it before proceeding. Everything else depends on it.
- 2 Is the airflow path open or ducted? Open paths with minimal restriction favor axial fans. Any ducted system generating above about 400 Pa usually favors centrifugal. See our industrial fan selection guide for the full Airflow-Pressure-Space framework.
- 3 Is the airstream clean or contaminated? Clean air: axial or backward-curved centrifugal both work. Dirty, sticky, or chemically reactive air: centrifugal, and select wheel geometry to match the contamination type.
- 4 What are the noise and space constraints? Axial fans are compact but louder. Centrifugal fans need discharge clearance but run quieter in most configurations. If noise is a hard constraint, review acoustic data before finalizing fan family.
- 5 What does long-term maintenance look like? Axial fans have fewer components and simpler service requirements. Centrifugal fans require more attention to impeller and bearing condition but handle harder system conditions more consistently over time.
If your answers point toward axial but system resistance is above 400 Pa, go back to question one. That number decides more than all the others combined.
Common Selection Mistakes to Avoid
Fan curve annotation: where common selection mistakes happen
Sizing by free-air airflow alone. Free-air CFM or m3/h tells you what a fan can deliver with zero resistance. Real systems have resistance. A fan that looks adequate on a catalog page may deliver 30 to 50% less airflow in the actual installation. Fan CFM calculation is here.
Using axial fans above their static pressure range. This is the mistake in the paint shop example. The airflow rating suggested the fan could handle the job. The static pressure rating said otherwise. Always check both numbers, and always verify them against the real system resistance. Not an estimate. Static Pressure Explained is here.
Substituting a forward-curved centrifugal fan in an open application. A forward-curved centrifugal in a near-zero-resistance, unducted installation will overload its motor because the power curve can continue rising toward motor overload in that condition. If the application is open, use an axial fan or a backward-curved centrifugal.
Ignoring contamination load in fan family selection. An axial fan in a heavy-dust exhaust application will accumulate deposits on blade leading edges, degrade aerodynamically, and eventually develop balance problems. If the air is dirty, select the fan family and wheel geometry to match.
Treating the fan datasheet as the system answer. The datasheet shows what the fan can do. The system curve shows what the fan will actually do in your installation. These are different things. See our how to read a fan curve guide for a practical walkthrough of how these two curves interact.
Frequently Asked Questions
Q: Which is better, an axial or centrifugal fan?
A: Neither fan type is universally better. Axial fans are better for high-airflow, low-resistance applications such as open ventilation, equipment cooling, and condenser airflow. Centrifugal fans are generally the better choice for systems with real resistance: ductwork, filter banks, exhaust systems, and process air applications where static pressure approaches or exceeds roughly 400 Pa. The right answer depends on system resistance and airflow path geometry, not on which fan type sounds more capable.
Q: How do you tell if a fan is axial or centrifugal?
A: An axial fan discharges air in the same direction as its inlet, parallel to the shaft. The blades are mounted on a central hub and look similar to a propeller. A centrifugal fan discharges air at roughly 90 degrees to the inlet direction through a scroll-shaped casing. If the inlet and outlet point in different directions, the fan is centrifugal.
Q: What are the disadvantages of axial fans?
A: Axial fans perform poorly in high-resistance systems. As static pressure increases, an axial fan’s delivered airflow drops sharply and efficiency falls. Axial fans also produce more broadband noise than centrifugal fans at equivalent duty points, and they are more vulnerable to performance degradation from contamination buildup on blade leading edges.
Q: What are the disadvantages of centrifugal fans?
A: Centrifugal fans cost more to purchase and require more installation space because of their scroll casing and 90-degree discharge geometry. Maintenance is more involved, particularly for impeller inspection, balance checks, and bearing service. In open, low-resistance applications, centrifugal fans are overspecified and less energy-efficient than axial fans for the same duty point.
Q: Can centrifugal fans handle dusty air?
A: Yes, centrifugal fans generally handle contaminated air better than axial fans, but wheel geometry determines how well they hold up. For heavy dust, sticky particulate, or fibrous material, radial-blade centrifugal fans resist deposit buildup and imbalance better than backward-curved or airfoil designs. Per ISO 1940-1, contamination-induced rotor imbalance is a primary cause of early bearing failure in industrial exhaust fans.
Q: What kind of fan moves the most air?
A: Large axial fans move the highest absolute airflow volumes. Industrial axial designs deliver more than 800,000 m3/h in tunnel, mine, or large-building ventilation applications. Centrifugal fans reach somewhat lower peak airflow volumes, but they sustain that airflow against system resistance that would cause an axial fan to stall or drastically underperform.
Q: At what point does duct resistance rule out axial fans?
A: In practice, axial fans typically start losing the efficiency argument around 400 Pa of system resistance, and the reliability case for axial becomes difficult to make above roughly 500 Pa. At those pressures, delivered airflow commonly drops 20 to 40% below the free-air rating, and motor loading climbs. Above 1,000 Pa, axial fans are rarely a viable choice. If your calculated system resistance is approaching 400 Pa, verify the estimate against real duct geometry before finalizing any fan selection.
Q: When should I choose centrifugal over axial for HVAC?
A: In ducted HVAC systems with meaningful duct runs, filter banks, cooling coils, and multiple distribution branches, centrifugal or inline centrifugal fans are usually the better choice because they maintain airflow against the resistance that ductwork creates. See our centrifugal fan for HVAC guide for application-specific selection guidance.
Q: What is the lifespan of a centrifugal fan?
A: In clean air with proper maintenance, a well-built centrifugal fan runs for 80,000 to 100,000 hours before bearings need replacement. That’s roughly 10 to 12 years at continuous operation. The figure drops sharply in contaminated environments. Dust and abrasive particles build up on the blades, create rotor imbalance, and push bearings into early failure. We’ve had customers in cement handling and woodworking operations replace fans every three to four years. Not because the fan design failed. Because abrasive airstreams without adequate pre-filtering destroyed the bearings early. The fan type matters less than the operating conditions and maintenance schedule. Monthly vibration checks and annual impeller cleaning are the two practices with the most impact on service life in industrial exhaust applications.
Q: What is the difference between a centrifugal fan and a radial fan?
A: The terms are often used interchangeably, which creates confusion. A radial fan has flat, un-swept blades extending straight out from the hub with no forward or backward curve. A centrifugal fan is the broader category and covers backward-curved, forward-curved, backward-inclined, airfoil, and radial blade types. In practice, radial-blade fans are chosen for contaminated, abrasive, or high-temperature airstreams where curved impellers accumulate deposits and lose balance. A paper mill or grain handling installation would typically specify a radial-blade design. A commercial HVAC air handler would go with a backward-curved or airfoil centrifugal fan for efficiency.
Need Help with Fan Selection?
If your project sits in the 100 to 500 Pa range, or if the airstream involves dust, heat, or chemical exposure, the right fan family isn’t always obvious from a datasheet. Proventofan’s engineering team works through these decisions every week across factory ventilation, process exhaust, and OEM applications.
Send us your system parameters — required airflow, estimated static pressure, airstream conditions, and installation constraints — and we’ll come back with a fan family recommendation and a shortlist of suitable models. No obligation. See our industrial fan selection guide , axial fan and centrifugal fan to prepare your inputs, or contact Proventofan directly.
References
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AMCA Standard 210: Laboratory Methods of Testing Fans for Certified Aerodynamic Performance Rating Industry standard for fan aerodynamic performance testing and rating at controlled conditions. Read more
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AMCA Fan and System Curves with FEI – Practical guidance on operating point selection Practical guidance on understanding fan and system curve intersections and fan efficiency index calculations. Read more
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API STD 673: Centrifugal Fans for Petroleum, Chemical, and Gas Industry Services API standard covering centrifugal fan requirements for industrial exhaust and process air applications. Read more
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ISO 1940-1: Mechanical Vibration – Balance Quality Requirements for Rotors in a Constant (Rigid) State International standard for rotor balance quality requirements relevant to fan impeller specifications. Read more
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U.S. Department of Energy / NREL: Improving Fan System Performance DOE sourcebook identifying system resistance estimation as a leading cause of fan energy waste in industrial ventilation. Read more
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ASHRAE Standards and Guidelines HVAC industry standards including guidance on air distribution system design and fan selection. Read more
For project-specific selection, consult a qualified engineer.
