There are vertical, black stripes all over the insides of the exterior walls of my house. I’m sure it’s mold. How do I get rid of it?
What you describe is most likely soot, which deposits on the walls in stripes where framing studs are located, in a flame-like pattern above baseboard convectors, in dots where nails are located, or as circular stains on ceilings above light fixtures.
You can test the stain by rubbing it with a little bleach on a paper towel; if the black color remains, it's soot, and if the color goes away, it's mold. Repaint soot-stained walls and avoid burning jar candles, which can emit a lot of soot, particularly after the candle has burned down about halfway.