An airbrush booth is a box with a fan and a filter that pulls overspray away from your face and, usually, out of a window. Airbrushing atomises paint into particles fine enough to hang in the air and settle on everything in the room, and a booth is the difference between a hobby you can do at a desk indoors and one that has to happen in a garage with the door open.
What a booth actually removes
A hobby spray booth captures the visible overspray: the pigment and medium that miss the model and would otherwise settle on the desk, the keyboard and your lungs. With water-based acrylics, which is what most miniature painting uses, that is the bulk of the problem, and a booth vented out of a window handles it well. What a hobby booth does not do is scrub solvent vapour. Lacquers, enamels and their thinners release fumes that a filter does not capture, and for those a booth is a partial measure rather than a solution.
Vented or filtered, and why it matters
Booths either vent through a hose to a window or recirculate through a carbon filter. Venting is far more effective because the overspray leaves the room entirely; the cost is that you need a window and you lose heat in winter. A filtered booth is more convenient and more portable, and it is a compromise: it catches particulate well and vapour poorly, and the filter is a consumable that stops working long before it looks used. Anyone spraying regularly indoors is better served by a vented booth even though it is the more awkward option.
The alternatives, honestly
Plenty of painters airbrush without a booth by spraying next to an open window with a fan behind them, and with acrylics that is a reasonable arrangement. A cardboard box will catch overspray if not remove it. What none of these do is protect the room from the fine mist that hangs after each pass, which is what a booth is really for. The decision usually comes down to where you paint: a dedicated space tolerates the mess, and a shared kitchen table does not.
Questions people ask about airbrush spray booth
Do I need a spray booth for airbrushing?
Not strictly, if you spray acrylics beside an open window. A booth matters most when you paint in a shared room, spray often, or use anything solvent-based.
Does a spray booth remove fumes?
A vented booth removes them from the room; a filtered one mostly captures particulate rather than vapour. For lacquers and enamels a booth alone is not adequate ventilation.
Vented or filtered spray booth?
Vented is considerably more effective because the overspray leaves the room. Filtered booths are more portable and rely on a consumable that degrades before it looks spent.