Building a paint booth
The booth needs to have good lighting and ventilation, but it also needs to be of a sufficient size for the job at hand. When you paint a car for example, you do not want it to be so small that you can barely get around the car, and you are at risk of damaging your nice paint with a zipper or a careless movement. You don't ever want to be struggling to be getting around the car safely.
The more light, the better. You can not have too much light, but if you do not have enough light, then you can not see the paint lay down, which can easily lead to runs and orange peel. In addition to good overhead lighting, get a good portable light that you can move around to better see what you are doing.
 Air compressor
When buying a compressor ask yourself how long you are going to be in the hobby. The low cost high HP compressors make air by using a smaller compressor run at high rpm. This beats the pump to death. These compressors will work for the guy who is dabbling some in the garage, but will fall apart if used regularly.
Motor HP has been incorrectly stated in the past. A 5 HP rated compressor sometimes used a lower HP motor rigged to pull more torque at start. This was often connected to a lower quality pump and run at high speed to produce higher CFM. These units seem to make more noise than air.
The true HP rating of a motor may be revealed by its current draw. A real 5 HP motor pulls about 22 amps while the 7.5 HP motor will draw 32 amps. Keep in mind the current these motors draw will cost you in electricity. I would avoid 7.5 HP units if that level of volume is rarely needed. The higher current draw will run up your electric bill if you use it moderately to run power tools.
An example: At a shop where the compressor was used daily, a quality Ingersoll Rand 7.5 HP compressor eventually burned out its bearings. For this unit IR used the same compressor pump as with the 5 HP version. With the 7.5 they got the increase in volume by using a larger pulley and ran the pump at a higher RPM. It also needed its belts changed every couple of months. In addition, this unit needed its magnetic stater replaced several times due to the levels of current required to start the motor.
 Air volume vs. uses
HVLP guns need air. The 1/4" quick couplers do not flow air well. The 3/8" couplers flow twice the air. The problem with the smaller coupler is that you start out with higher pressure and since the couplers can not flow the air, you get a drop in pressure. You have to change your rate of movement to compensate and that is not easy to figure out as a beginner.
 Piggybacking two compressors
One compressor air volume issue was solved by using two 110V compressors. The first one's a 3hp, 10 gallon tank putting out 7.2 CFM @ 40 psi and the second one's a 2hp, 10 gallon tank that puts out about 4 CFM @ 40 psi.
These were run on different circuits so they would not trip the circuit breaker. A 20 foot hose was run from each air compressor, allowing the air to cool and water to condensate out. They flow into a Y-connector at my high volume water trap. The water trap has an air regulator and 50 feet of hose that goes into the paint booth.
I never ran out of air with myTghis set-up was able to supply enough air to run a gun that required 9.5 cfm @ 29 psi. On long spray sessions the smaller compressor turned on to keep up with demand but it normally only required the larger compressor. One advantage of this type of set-up is you do not have to deal with supplying a 220V circuit for a larger air compressor.
Air flow within the spray booth is necessary for a good job and to prevent build-up of paint vapor. The goal is to move overspray out, maintaining visibility and avoiding overspray landing on completed areas. A couple of little box fans and a small hole in your tent will not cut it. The box fans will draw air back into the booth around the box corners. The corners should be filled, opening up the tent to allow for lots of air flow. A whole house fan and lots of holes in the tent work well. Do not worry so much about the dust; most of which comes from the part being painted as well as the painter.
More air is also a safety issue. When using an organic-cartridge mask, the less lingering paint/solvent vapor, the better. Organic cartridges need to be fresh. They have an expiration date on them and the charcoal fills up eventually. The biggest exposure to bad chemicals is though the skin and through an improperly fitting mask. A supplied-air system and coverall suit is a good way to go. The fresh air units are pricey, but they maintain good resale value, so think of it as a rental. The suits are cheap and cut down on the dust that comes from clothing.
If the booth is attached to a home, care must be taken to ensure that the occupants are not exposed to fumes. Use out-flowing fans to create a negative pressure (suction) in the garage area. You might be surprised at the pressures that small and medium sized fans can produce. Try using a roof vent fan inside the painting area (so the fumes aren't drawn from the paint area into the dwelling) to pull air out.
 Resources and references
- How to build a paint booth at home from mckennasgarage.com
- How to Create a Paint Booth in Your Garage from wikihow
- How to build a paint booth from ehow
- The paint booth from theairplanegarage.com
- How to build a paint booth from interlog.com
- Paint booth from interlog.com
- Make shift paint booth HAMB thread
- Hotrodders knowledge base
- Hotrodders forum threads