Synopsis: Jeff Jewitt explains how to build a knock-down booth for high-volume, low-pressure spray equipment that will safely ventilate your workspace. A knockdown booth is inexpensive, can be set up easily in a basement or garage, and stored out of the way. The ventilation system he uses is an explosion-proof motor driving a non-sparking aluminum fan. He explains how he built this booth and system and which accessories add conveniences worth pursuing.

Spraying a finish in a basement or a garage 20 years ago was risky business. High-pressure sprayers and flammable finishing materials were your only choices, and spraying these without proper ventilation was begging for a disaster. Not only did the risk of a fire or explosion loom large, but overspray was bound to settle on every horizontal surface in the immediate area.

With new high-volume, low-pressure (HVLP) spray equipment that drastically reduces overspray and with new water-based finishes, spraying finishes at home or in a small shop has become a viable option. One problem remains: how to ventilate the overspray. While water-based finishes are less problematic as fire hazards, the buildup of atomized finish and solvent can still be a health hazard. Spraying in an enclosed space without proper ventilation is unacceptable, so that leaves you with only a few options:

• You can spray outdoors. The problem with this alternative is that dust, bugs and other airborne debris will often ruin your wet finish. Also, strong breezes may prevent the atomized spray from landing where you want it.
• You can spray within a well-ventilated area, such as a screened porch. This is better because you minimize the possibility of debris landing on your wet finish, and the force of sudden breezes is reduced; but you still have overspray to worry about.
• You can spray in an enclosed area, such as a basement or a garage, and exhaust the fumes with a fan. However, basement windows are usually too small to fit a fan that will move enough air, and many garages don’t even have windows. A small, portable spray booth solves these problems.

A knockdown booth may be the answer Professional refinishers use specially designed spray booths to exhaust fumes in their shops, but these are quite costly, with prices starting at about $10,000 and moving upward, depending on all of the bells and whistles. These booths can also take up a large amount of floor space. The knockdown version I made can be built for much less (about $550). It can be set up easily in a garage or a basement with a large window and stored out of the way when not in use.

From Fine Woodworking #139

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