Folks have talked about the incense test and while this may work for them, in my opinion, incense sticks do not create enough volume of smoke to do much good.
An easier way is to use a couple of sheets of paper towel, rolled tightly in a bundle. Light one end, wait for it to burn down a bit (10 seconds or so), then blow out the flame. Move the bundle around your entire work area and watch how the smoke behaves. This will tell you where your “dead spots” are and where the active ventilation is. I recommend this method for people who are working with frits, powders and enamels.
This type of test is especially important if you do not have a hood or workstation enclosure (yet) so you can determine if your “makeshift” ventilation is working, and if not, how to adjust it by moving your fans around.
Be sure you are sitting behind the torch in your usual torchworking position while you are doing this test!