Frequently Asked Questions

Below are just a few commonly asked questions. If you’ve got a question of your own don’t hesitate to contact us.


What is the difference between an axial and centrifugal fan?

For an axial fan the air flows parallel with the shaft that the fan wheel is attached to. The housing is typically cylindrical and installed in the system like a piece of duct.

For a centrifugal fan the air enters the side of a scroll-shaped housing and is slung off the fan wheel to an outlet on the fan housing. Axial fans are typically used in high volume/low pressure applications. Centrifugal fans can develop higher pressures as well as provide high volumes.

What are the fan or affinity laws?

These laws express the relationship between variables (pressure, flow, shaft speed) involved in fan performance and power. Fans are tested at a specific design point and then the fan laws are applied to generate a fan performance curve. These laws will tell how a fan will perform under different conditions.

What size fan do I need?

Fans should be picked only after the system it will be connected to is designed. Fans simply perform the work of the system and are frequently misapplied.

What material should my fan be made of?

There are a few things to consider before building a fan. Determine the corrosiveness of the environment as well as the air stream. Next, does the application involve high temperature? Do you need spark resistance? Are there chemicals or corrosive elements involved? Lastly, is the airstream abrasive?

Fans are most commonly made of carbon steel and then receive a coating. Fans can also be made of aluminum, stainless steel and fiberglass or even carbon fiber.

Should I choose a belt drive or direct drive fan?

Both options have their own pros and cons however direct drive is typically the preferred setup from a maintenance and performance stand point. A belt driven fan’s performance can be adjusted by changing the drives but if a fan is properly selected from the beginning then a direct drive fan is usually a good fit.

Should my fan have a VFD?

VFD technology has come a long way just in the past 5-10 years. They are more reliable and are more economical than most people think. A VFD is the ideal starting method for eliminating startup inrush and also allows for a level of controllability.

Dust Collection:

Do I need a dust collector?

Dust collectors in most cases are necessary. Depending on your process and the type of dust being generated, a dust collector may be required by OSHA, DEP or any other AHJ. Dust collectors help maintain a clean working environment as well as control air quality.

Is my dust explosive?

Believe it or not, most dusts are explosive. NFPA states that if a dust has a Kst value greater than 0, then it is considered explosive and specific requirements need to be met in order to protect the system. The only way to determine the Kst value is to have it tested by a laboratory. Particle size also plays a big role in how explosive a dust is. Typically the smaller the size the higher the Kst value.

What NFPA Standard should I use?

NFPA 654 is the ‘Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids’. Depending on your specific dust or process, you may have to comply with other Standards as shown in Chapter 1 of NFPA 654.

Can dust collectors be used for fumes?

Yes! Dust collectors are perfect for all sorts of fumes. These include welding fumes, soldering fumes, laser or plasma table fumes and many more.

Can I recirculate the air from the dust collector back into my building?

Yes. Air recirculation is especially important when the area is a conditioned space. However, if the dust is explosive specific measures have to be taken in order to protect the system.

Client Testimonial

Markair has been a go-to provider on several major projects that required customized solutions for highly technical applications. I would not hesitate to recommend their services to anyone that needs industrial fan equipment.

Forrest J. Masters, Ph.D., P.E. University of Florida Department of Civil & Coastal Engineering

When it comes to equipment reps, working with Jason is a different experience. You are not just dealing with a sales guy, you are dealing with a full service company who will help you see your job through from conceptual design to final construction close-out. Without hesitation, he is the first person I call for all of my projects.

Cassie Anderson, P.E. CH2M Hill