Commercial spray booths are great for applying finishes in a controlled atmosphere, but most people find them too expensive to use at home. However, if you are using a High Volume Low Pressure (HVLP) spray gun indoors without a spray booth, you are exposing yourself to harmful chemicals. Follow the steps below to build a simple, inexpensive and effective spray booth in about a day. Your lungs will thank you.
Buy or find a fan with a separate motor. That way, the fan can be connected by a fan belt in the spray booth, with the motor housed in an upper box to prevent it from getting covered in over spray. Your fan can be as big as you want, but the more air you move through your spray booth, the more air you will have to replace in your shop and the quicker your shop temperature will change. Get a 1/4 horsepower explosion-proof motor to power the fan unless you are only spraying water-based finishes. In that case, the motor doesn't have to be explosion proof.
Build a plywood box to house the fan. The box should be about a 30 cm (1 foot) deep, open at both ends and big enough to fit the fan on one end and a furnace filter on the other. Cut a 5 cm x 10 cm (2 x 4 inch ) board to length and attach it to the center of one end. Then mount the fan to the center of the board. Cut two strips of narrow wood for the other end of the box, and attach one to the top and one to the bottom to keep the furnace filter from being sucked into the fan while the spray booth is operated. Finally, attach four button catches to hold the filter in place.
Cut a notch in the top of the box that is big enough for the fan belt to fit through, and bolt the motor to the top of the box. Then, build a box around the motor to shield it from over spray. Leave a space in the box for the electric cord to exit.
Place the box in an open window and build a small stand to support it if necessary. Seal any open spaces around the box to maximize the air flow in the spray booth.
Hang plastic curtains on either side of the window to create an open-ended tunnel, about 2.4 m (8 feet) long and wide enough for you to fit inside while you are spraying. Hang the curtains on a track so they are easier to push out of the way when you are not using the spray booth.
Plug the motor in, pull the curtains shut, load up your HVLP spray gun and you are ready to spray.
Replace the filter often, and clean or replace the curtains and fan box if they become caked with finish. Check your home owner's insurance policy to find out whether your rates will be affected by spraying at home.
Wear proper respiratory protection when spraying finishes, even with a spray booth. If you use a type of spray gun other than HVLP, this spray booth might be inadequate. HVLP guns produce less over spray than other types of guns, so they require less ventilation.