Semi Down Draft Powder Coating Spray Paint  Booth

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Marathon’s Semi Down Draft Series spray booths are designed to be an efficient finishing solution, an excellent balance between cost, quality and functionality. This model can be ordered with a Spray & Cure Air Make Up unit (heater) or without.

Semi Down Draft

The Semi Down Draft Spray Paint Booths is an excellent “All Around” paint booth, and is also one of our most popular styles. The air enters through the intake plenum above the front doors, and travels horizontally through the booth.

The air exits the booth through the rear exhaust filter plenum, and finally out the back of the booth. This standard design is popular because it is simple to use and maintain. You can order this design with a Spray & Cure heater added as an option. This model is available in standard sizes, or Marathon can custom build one to your specifications.

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adding one of our
Spray & Cure
heating systems
to your booth
order, or to an
existing booth
as an UPGRADE!

  • Automotive Semi Down Draft Slide Show
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  • Automotive Semi Down Draft Slide Show
  • Automotive Semi Down Draft Slide Show
  • Automotive Semi Down Draft Slide Show

The Semi Down Draft “(SD) Series” Spray Booth
This spray booth is designed so the air enters through the front ceiling intake filters and moves horizontally, from the front of the booth to the rear of the booth, enveloping the vehicle with clean, filtered air. Over spray from the painting process is then captured by the exhaust filters in the back wall of the spray booth.

While Marathon Finishing Systems offers a full line of paint booths, the Semi Down Draft Spray Booth is by far our most popular model, one that strikes an excellent balance of utility, price and air flow type. Marathon designs and manufactures our entire line of spray booths to meet today’s demanding paint technology. Whether you are spraying solvent-based product (paint), waterborne product only, or a combination of solvent and water borne product, we have the right solution for your application. Our team will help you choose the right spray booth package for your application and facility. We can also custom design a specialized system, based on your specific requirements. In fact, most of the systems built and installed by Marathon Finishing Systems are custom engineered for our customers. If your budget is the determining factor in your decision, you will not get a better “Bang for your Buck” than our Semi Down Draft Spray Booth.

If you’re refinishing cars, small trucks, motorcycles, watercraft, Marathon Finishing Systems will design, manufacture, deliver, install, and then train your staff to properly operate and maintain the complete system. Or if you choose, you can also install the booth yourself with our installation instructions.

Why choose Marathon over our competition?

Here are just a few reasons why:

1. Our spray booths comply with all national (NFPA 33) environmental, fire, and safety codes.

2. Marathon’s spray booths are “Waterborne” ready or always upgradable.

3. Our booths are all Nut & Bolt type construction. No zip (sheet metal) screws!

4. It’s all about the lights! We deisgn our all of our booths with horizontal lighting fixtures (where possible), to help eliminate shadows.

5. We use only “Inspection Grade” LDPI, Inc. brand light fixtures made in the U.S.A. for spray booth applications.

6. Our Spray & Cure heat systems are manufactured in the U.S.A. Energy Efficient and “LISTED” for compliance.

7. All of Marathons products are manufactured with “Top Brand Name” components, made in the U.S.A.


Marathon sets the Benchmark every year with new product releases and smart booth designs, all for an honest price! This is what you can expect from Marathon Finishing Systems.

Intake, heated booth: Outside air is filtered twice, once as it enters through the air make up unit located at the side of the booth, and again as it passes through the intake plenum filters (shown in green). In this example, this booth is equipped with a Spray & Cure heating unit.
Semi Down Draft Airflow Diagram
Intake, non heated booth:
The air is filtered twice, once through plenum side filters, and again through the ceiling filters before entering the work area.
Semi Down Draft Airflow DiagramExhaust: The filtered air travels horizontally across the length of the booth (crossflow). Finally, the air is filtered of overspray and particulates by the exhaust filters before exiting the booth. Marathon uses standard size intake and exhaust filter media, readily available from most paint and refinishing suppliers.


Standard Series Spray Booth
The Standard Series Booths are designed with one simple concept in mind; good quality and design for a competitive price!

Basic Standard Features That Set Marathon Apart
Horizontal “Shadow Free” lighting located in side walls from LDPI, Inc., Dual skin “Barn” product doors, Dual Skin Man Access Door with a large Observation window, “Dayton” Fan from Grainger, “Dayton” High Efficiency motor from Grainger, G.E. Electrical Controls, Goyen air valves.

Construction and Design
All of Marathon’s Standard Series Booths are manufactured using 18 gauge galvanized steel on precision CNC equipment. Our booths are Nut & Bolt type construction, precision punched 6″ on center and 2″ companion flanged for easy assembly in the shop. Built according to NFPA Codes and OSHA national requirements.

Why are Marathon products so RELIABLE?
Marathon DOES NOT build our own fans, motors, light fixtures, heaters, and control panels like some “others”. We ONLY supply U.S. Made TOP BRAND NAME components that you can rely on and service easily. All fans and motors are available in any Grainger branch in your local city, or online. Marathon’s light fixtures are manufactured by LDPI, Inc., our controls are by G.E. and all heaters are ETL Listed with a 2 year warranty on all parts.

Marathon Goes the Extra Mile for Our High Quality Products!
Manufactured in the US by LDPI, Inc., they are standard 48″ long, 4-Tube, 32 watt, T-8 fluorescent fixtures, with electronic ballast, dual voltage 120v/277v, U.L. listed for this application.

The Standard Series Booths are designed with horizontal lights in the side wall and hip panels for shadow free lighting. Some of our “cheap” competitors build their booths using 1 or 2 vertical lights in the side wall of the booth, because it’s cheaper to build it that way. All Marathon booths have horizontal light fixtures that run along the length of the spray booth, NOT up and down!

Product and Man Access Doors
Another standard Marathon feature is that our doors are all built with two skins (Dual Skin) not one. That means the main product and man access doors are smooth on the inside and the outside of the door. Like a steel door (fire door) should be. Our man access doors have a observation window. The cheaper booths have single skin doors with the flanges (structure) on the inside of the booth. This “Tin-can” door is flimsy and collects dust and over spray on the open flanges. It also “wobbles” when you open and close the door. All of Marathon’s doors are “Jig built” to last and use tube steel for extra strength.

Air Filtration
Marathon spray booths use only “Industry Standard” sized filters. Easily replaceable from your local paint store, filter supplier, online, or you can always call Marathon. The Standard Series Booths come with “20 x 20″ x 2″ hi-efficiency fiberglass paint arrestor pads (exhaust filters) and 20″ x 20″ x 1” premium “Tackified” intake filters with scrim backing and an internal metal frame.

Fans and Motors
Marathon’s fan and motor packages come from a long established and well trusted source; Grainger. These packages are U.S. manufactured, AMCA certified, spark resistant aluminum blades, hi efficiency 3-phase motors 208/230/460v (230v single phase available). With belt-driven tubeaxial fans, the streamlined belt tunnel ventilates the drive compartment with air from outside the fan. The steel housing is iron phosphate-processed for rust protection, and has a durable acrylic epoxy paint finish. The factory installed cast-iron sheave is assembled directly on the fan shaft. All Motors and belts are packed separately when the complete fan with drive package is ordered. Mounted either vertically or horizontally, these crucial components have permanently lubricated ball bearings for a long service life. The precision-balanced, aluminum AMCA Type B spark-resistant propellers and belt guards eliminate the risk of fire or explosion. Max. inlet air temp.: 200°F Max. ambient: 104°F.

Parts and Accessories
Marathon booth packages are supplied with a manometer, All required nuts & bolts, gaskets, caulking, tempered glass for light covers, instruction manual, assembly drawings, wiring diagrams, and Marathon’s factory support and expertise. We live spray booths!

Marathon offers a manufacturer’s warranty on all spray booths for 1 year.

Built to last, Great Finishes Start with Marathon!

Product Options

Product Options and Upgrades
(available with most models)
Marathon Finishing Systems offers a wide variety of options and upgrades for you to choose from. The standard booth configurations that are shown in our product pages are just a starting point. Every environment is unique, and every production line has it’s own special requirements. Listed below are some of the various options that you can add to your equipment order, although certainly not everything. We can custom engineer any solution you may require, so we know that no list can be complete. This list shows the most common options and upgrades, so if you don’t see what you want here, just ask us…

• Insulation
While the standard booth is a single wall, non insulated panel construction, we can also build your booth with double wall, insulated panels. These panels contain standard fiberglass insulation filling a center channel between two steel walls. While we do not recommend this type of upgrade, there are certain applications where it is appropriate. We can help you determine whether you need single or double wall panels.

• Doors
When we engineer a spray booth or oven, we usually configure the main product doors so that they are around 3 to 4 feet wide, so that they are easy to open and close, and do not weigh too much. This almost always turns out to be a “Barn Door” configuration. However, if you you need to have a specially designed door configuration to meet specific requirements (to fit in a certain space, for example), you can choose from a wide range of door styles:

  1. Tri-Fold
    A single opening is covered by three doors that can have a single door on one side, and two on the other. The single door can be opened and closed independent of the other two. Or if you choose, you can have all three doors open and close “Accordion Style”, in which all three doors are connected (and still have a single panel act as an independent single door).
  2. Bi-Fold
    A single opening is covered by two sets of doors, each having two panels and hinged in the middle. Each set can be opened independently of the other.
  3. Roll Up
    This type is the standard roll up door that you would see on a garage or industrial unit. The whole door lifts from the bottom and rolls up at the top.
  4. Custom
    Don’t see what you’re looking for? No problem! We can custom design and manufacture virtually any kind of door you may need, just tell us what you’re looking for, and we will find or fabricate it. Most of what we do is custom work, so you might say: It’s what we do.

• Windows
There are many standard size windows, from a small 10″ x 12″ “Peek In” window, up to a full size 36″ x 48″ “Observation” window. These windows can be placed in doors or wall panels of the booth to fit your needs. We can even make custom sized windows, and engineer them into your booth wherever you need them.

• Control Systems
As the various options that you require are added to your booth, the control options become more complicated. While it can start out with a simple “On-Off” switch, it can end up requiring a fully digital system with a touch sensitive display screen and computer control system. Not to worry! We can engineer the entire system to easily control all aspects of your equipment, while keeping the daily operations simple, yet effective. We will even show you how to properly operate each and every function, so that you can get right to work.

• Lighting
Marathon takes great care when calculating all aspects of illumination (location, distribution, orientation, etc.) for all of our spray booths, so that you get a “Shadow Free” and brightly lit work area. If you would like the ability to increase the amount of light that may be required for your application, we can add as many lights as you would like. If you would like to change the type of light fixtures (change an Open Type to a Class I Division II, for example), you can select from the many types of lights available. We supply lighting fixtures from LDPI, which come with a full one year warranty.

• Motors
While Marathon takes great care in making sure that the fans and motors that we engineer into our booths are adequate to the task of moving the air through the booth in the proper fashion, you may want to increase the horse power of the motor, or increase the size of the fans to meet a specific environmental requirement. We can accommodate such a request, and make sure that the delicate balance of intake and exhaust is appropriately maintained. We use only American made fans and motors, from the best manufactures in the country (such as Dayton, Hartzell and Weg). These parts come from directly from Grainger, so they are easy to locate and replace. They also come with a full year manufacturer’s warranty.

• Filters
One of the major functions of a spray booth is to remove overspray from the air stream before the air is exhausted from the booth. Another is to remove airborne particulates from the air before it is brought into the work area of the booth. Marathon uses standard intake and exhaust filters, readily available from most paint and filter suppliers. Both types of filters can be upgraded to a higher level of filtration, including NESHAP and HEPA, as well as filtering out harmful components from the use of chromates. The choices for filtration are many. Marathon can help you decide what filtration components are right for your application.

• Cooling Systems
Everywhere on Earth is either too hot or too cold at some time during the year. Working in comfort is the key to maintaining morale and productivity. For those times when it is too hot, we can configure your equipment to establish and adhere to a specific temperature envelope. We supply Carrier components (which also comes with a full year warranty), and integrate them seamlessly into your control systems. Keep your cool when production heats up.

• Heat (Curing) Systems
The heating systems available for spray booths are meant to perform two functions:

  1. “Comfort” heating, to keep the environment warm enough for worker comfort.
  2. “Spray & Cure”, for use after painting to speed up the drying of the paint, and to harden the paint beyond what is possible at room temperature. These components are also American made by one of this country’s foremost manufacturers of heating components for the spray booth industry.

• Humidity Control
While the requirement for true humidity control is uncommon, we can configure a system that will maintain your target humidity with accuracy and repeatability. Humidity can only be controlled if you have full heating and cooling systems as well, so only consider humidity control if you are planning to control both heating and cooling.