Dave Nelson's advice is spot on. The risk is inhalation of so called sub pm10 particulate. These are the particles that are less than 10 microns in size and stay inside the lungs for long periods. A good half face respirator designed for painting will provide adequate protection as long as the respirator has a good fit to your face. Half face respirators do not fit properly if you have a beard or have not shaved recently.
if you can open an outside window and install a window fan exhausting from the room, it is a good idea, also. So called water based paints still contain some organic compounds albeit a lot less hazardous than xylene formulated paint such as the old floquil solvent based paint line.
Is there a cheap way to make a booth?
I know some modelers who claim that once you are dealing with water based paints, anything goes and no special precautions are necessary. I suspect the better view is that some precautions are wise.
If you do not use solvent based paints then your primary needs are to protect your lungs from the particulate matter that all paints emit. A simple "paper" mask is not as good as you can do, but better than nothing. Respirators are available at many good hardware or big box home project stores. Some are suited even to solvent based paints (which of course does not help others in the household, including pets) while others are less sophisticated yet adequate for water based paints.
Protect your eyes and glasses with safety goggles. Protect your hair with a cap or painter's cap. I'd wear latex or similar protective gloves as well even if the paint is not per se harmful. Ventilation is useful even if it means opening a window in winter.
The other need is to protect your surroundings from overspray and there spraying into a cardboard box might be sufficient. For certain purposes I saved a really large kitty litter jug (same plastic as milk jugs) and cut away a side to create a movable little booth. I use it to touch up the weathering on my track.
The fact is guys use airbrushes or rattle cans AND solvent based paints to paint and weather track and other such situations where a spray booth simply is not practical or possible. Ventilation and a respirator are maybe not the absolute ideal in protection but appear to be sufficient. After all check out your average auto body shop sometime!
Dave Nelson
I don't have one .Can't use garage in winter.Do you guys have any ideas I know it's not safe with out a paint booth but I don't paint often and use only water base paints. A fan with a window open perhaps? thanks rambo1..AND HAPPY NEWYEAR TO ALL.