"Aren't a fan and a blower the same thing?" is a question people outside of this industry ask often, and it is a fair one. On the plant floor, the words get used interchangeably, and most of the time that is fine. Nobody is going to correct you for calling a centrifugal unit a blower during a walk-through.
But there is a real technical line between the two, and it starts to matter the moment you are specifying equipment. Get it wrong and you can end up with a unit that is working harder than it should, or one that never had the pressure to do the job in the first place.
The Real Difference: It's About Pressure
A fan moves a large volume of air against relatively low resistance, up to a pressure ratio of about 1.11 (ASME's threshold). A blower does the same basic job, moving air, but is built and operated to develop higher pressure, generally somewhere in the 1.11 to 1.20 range. Go higher than that and you've crossed into compressor territory.
A blower is not really a separate category of machine sitting apart from fans, but rather a fan engineered and operated for higher static pressure. That is why a high-pressure centrifugal unit so often ends up called a blower, while an axial unit usually keeps the plain "fan" label.
It helps to think about your own system. The more resistance the air must push through, like filters, long duct runs, or tight bends, the more pressure the equipment needs to develop, and the closer you move toward blower territory. A system with almost nothing in the way of the airflow rarely needs true blower pressure, no matter what anyone calls the unit moving that air.
Why the Words Get Used Loosely, and Why That's a Problem When You Spec
Using these terms interchangeably only becomes a problem on a spec sheet, where a mismatch between the word you used and the pressure your system needs can leave you with equipment that underperforms from day one.
The fix is simple: do not get hung up on the label. Get the pressure and airflow numbers right first, and the correct type of equipment follows from there.
Matching the Type to the Job
High volume, low resistance. Axial designs, sometimes called axial fans and occasionally axial blowers in the field, are the right fit for general ventilation, cooling, and straightforward air exchange where nothing much is standing in the way of the airflow.
Higher resistance, ducted or filtered systems. Centrifugal designs, commonly called blowers, are built for air that must move through filters, scrubbers, or long duct runs where resistance builds up along the way.
High pressure, demanding process air. Pressure blowers and high-pressure radial blade designs, like Hartzell's Series 07 and 07T turbo blower line, are built for the genuinely high-static applications where a standard fan won't keep up no matter how hard it runs.
Figure out your static pressure and airflow requirement first, and the fan-versus-blower question answers itself.
Get the Numbers Right, and the Equipment Follows
Specifying by label instead of by pressure is how plants end up with equipment that underperforms, or that works harder than it needs to, just to keep up. The fix is not a better vocabulary. It is knowing your system resistance and letting that number drive the decision.
If you want a second set of eyes on your numbers, our engineers are glad to walk through the application with you.
Call 1-800-336-3267 or email info@hartzell.com, and we will help you land on the right type.
FAQ
Are a fan and a blower the same thing?
Technically, a blower develops higher pressure than a standard fan.
What is the technical difference between a fan and a blower?
It comes down to pressure ratio. By ASME's definition, fans run up to 1.11, blowers 1.11 to 1.20, and anything above that is compressor territory.
Is an axial blower different from an axial fan?
Usually, it is the same equipment. Blower just emphasizes higher-pressure duty, though axial units are typically still called fans.
Do I need a fan or a blower for my system?
It depends on your static pressure. High resistance favors a blower or centrifugal design; low resistance favors an axial fan.
Why is a centrifugal fan called a blower?
Its right-angle airflow path generates higher pressure, which is the defining blower characteristic.