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Q. How do I decide which airflow style is best for my paint booth?

A. Ultimately, when deciding upon an airflow style for your paint booth, you want to select the style that fits within your business’ budget and meets the quality requirements for the products you paint. You don’t necessarily need the best paint booth on the market or the most expensive booth. You want the paint booth that is best for your business, with an airflow style that allows your operations to be the most efficient.

The following are the four primary airflow styles for paint booths:

Crossdraft paint booths are generally less expensive up front and result in lower operating costs because they typically operate at a lower cubic feet per minute (cfm) airflow rate. They require smaller fans, smaller air make-up units (AMUs) and fewer filters. 

Air enters through a filtered front door or plenum, and is pulled horizontally — parallel to the floor and over the product — to the exhaust chamber at the rear of the booth. The filter bank captures particles, and the filtered air is exhausted into the atmosphere through ducting.

Crossdraft booths are easily pressurized for climate control. They also provide a versatile solution for a variety of coating applications — from wood products to aircrafts.

The biggest drawback of crossdraft paint booths is the increased chance of contamination. Since crossdraft airflow moves horizontally, floor contamination is possible. Contamination can also happen when painting parts, as the air flows across the ones closest to the intake filters and can flow across the top of other parts in the paint booth. There is also less control of overspray in crossdraft paint booths compared to spray booths with other airflow styles.

Side downdraft paint booths are an economical solution for businesses that cannot or do not want to invest in an exhaust pit.

In non-pressurized side downdraft paint booths, air flows downward over the product — drawn through a full-length, filtered ceiling toward the floor by exhaust fans located in exhaust chambers on each side of the paint booth. In pressurized side downdraft booths, an AMU or intake fan forces air into an intake plenum that encloses the full-length, filtered ceiling.

Gravity-assisted downward airflow is one of the biggest benefits of side downdraft paint booths, and they provide more uniform airflow than crossdraft booths. Side downdraft paint booths also offer a higher level of contamination control and finish quality than crossdraft paint booths, largely because of the downward airflow and side exhaust.

A larger footprint is unavoidable with side downdraft paint booths, as they require more exhaust fans, ducting and roof penetration, and the exhaust plenums on the sides increase the overall width of the spray booth. Operational costs of side downdraft paint booths are slightly higher than crossdraft paint booths due to the full-ceiling filtration. Also, as air gets pulled into the exhaust chambers on the sides of the booth, overspray can hit the painter.

Semi-downdraft paint booths are a hybrid, combining features of crossdraft and downdraft booths. They are generally less expensive than downdraft paint booths, with lower installation and operational costs.

Air enters semi-downdraft paint booths through a filtered ceiling plenum in the first 25 to 30% of the booth. The exhaust fan continues to pull the air through the working chamber, causing the air to change directions and become parallel to the floor. The air flows across the product and exits through a filtered exhaust plenum at the rear of the paint booth.

The only downside of semi-downdraft paint booths is the potential for dead airflow spots at the front of the spray booth, which can make spraying difficult.

Downdraft paint booths provide the best airflow style for controlling overspray and contamination. 

In downdraft paint booths, air enters through a filtered ceiling plenum in a downward motion, flows vertically over and around the product, and exits through a filtered exhaust pit in the floor that runs nearly the entire length of the paint booth. Unlike side downdraft booths, the airflow does not have to fight gravity or pass by the painter; rather, it is assisted by gravity, which carries overspray into the exhaust pit.

Downdraft paint booths require about 20 to 40% more air than crossdraft booths, adding to operational costs. However, the nature of the airflow in downdraft paint booths produces the fewest blemishes, with the least amount of buffing required. Such premium finishes may not be necessary for some industrial products, parts and components.

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