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Finishing Academy Paint Booth Training

Choose one of these Aerospace Refinish Training Modules:


1.1 Introduction

1.2 Crossdraft

1.3 Downdraft

1.4 Airflow

1.5 Filter Replacement

1.6 Temperature and Humidity - Controlled Booths

1.7 Equipment

1.8 Fire Protection

1.9 Conclusion

1.3 Downdraft


A downdraft booth allows air to enter the booth from the ceiling through intake filters and then to flow downward over the plane and into exhaust trenches located in the floor. The main trench in the floor is laid out in the same shape as the airplane’s shadow. If three stage filtration is required for metalized paints, the first layer is located just under the trench grating for easy access when changing. The other stages of filtration are located in the filter house.

The trenches allow the exhaust system to draw air from the floor level to a nearby filter room. Trenches can be a bit difficult to maintain with paint particles penetrating the first stage of filtration and impinging on the floor or other parts in the airstream. For this reason, the use of dampers or other moving parts in the trench is not recommended.

The filter house is built to allow for the trenches and the underfloor ducts to vent the contaminated air into the filter house. The air then expands and moves through the other two stages of filters. Exhaust fans are located on the clean air side of this filter house and discharge the filtered air above the roof line of the facility.

Advantages and Disadvantages

Downdraft paint booths require pits to be installed in the concrete floor, which add cost to the project.The most cost effective way to install a downdraft paint booth for airplanes is to design it into the facility from the start. The shadow trench be designed to allow for the plane’s wheels to have full support while moving into and out of the paint hangar and while being painted. On small planes this is not much of a problem, but with larger planes, it can be a design problem.

The advantage of a downdraft booth is airflow across the aircraft can be more uniform, especially on areas most visible such as the top and sides. Since the pits are also drawing air, there’s a tendency to not have low airflow areas underneath the aircraft, though some do occur.

The disadvantage of a downdraft booth is flexibility. Because the pits are below the aircraft and shadow its shape, the size and shape of the aircraft are important. The pits can be designed for a series of similar body aircraft; however, the sizes and shapes of the aircraft cannot vary as much as in a crossdraft booth.



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