One of the defining characteristics of a spray booth is what type of airflow it uses to remove overspray. The three basic types are open front booths, crossflow booths, and downdraft spray booths.
Open front booths have only three walls. They take in unfiltered air through the open front, through the work area, and into an exhaust filter at the back. These are the least expensive type of spray booth, and are sufficient for situations where the main concern is containing overspray. Open front booths are no help in preventing contaminants from getting into your finishes, since the air they pull in is no cleaner than the rest of your shop air.
Crossflow (or crossdraft) booths draw air in horizontally through an intake filter and pull it straight through the chamber to the exhaust filter on the opposite side. They expel the filtered exhaust into the room or vent it outside. These are the most common and least expensive fully-enclosed spray booths.
Downdraft booths pull air in through ceiling-mounted filters and direct it out in one of several patterns. In order of increasing effectiveness and price, they include:
- In modified- or semi-downdraft spray booths, the air flows down along the length of the booth and out the back.
- Side downdraft booths pull air down via filters that run along both sides of the booth at floor level.
- Pitted downdraft booths draw air straight down into a cavity underneath the floor.
Downdraft booths are usually more expensive than crossflow booths, but downward airflow does the best job of removing overspray from the work environment.
The majority of buyers choose open booths. The expense of adding intake filtration is significant, and in many situations it's overkill. However, exacting applications such as automotive or aircraft finishes and industrial coatings require precise tolerances. Filtered intake is essential for achieving the results those applications demand.
Filters
Intake and exhaust filters can last for years. To let you know when the filter needs to be replaced, the booth you buy should come with a manometer. Manometers measure the air pressure on both sides of the filter, and as the filter gets dirty, that pressure difference increases. When it hits a preset limit, the booth should indicate that it's time to install a new filter.
Some manufacturers require that you buy filters directly from them while others let you use generic filters you can buy at a paint supply store. While this isn't a critical factor, it can be convenient to buy replacement filters on your terms, not the manufacturer's. Make sure the filters you use are appropriate for the contaminants you're trying to remove: dust filters work well for large particles, but not as well for aerosols or fine mists.
Water-filtered booths used to be popular for heavy-duty painting applications since recirculating water trapped airborne particles without clogging up filters. These systems are rarely used any more, since improved environmental regulations have made disposal of the contaminated water much more expensive and difficult.
