I wanted to answer one of those car-camping questions that never seems to die: what really happens if you sleep in your car with all the windows closed? So I did it—cold, rainy, November vibes, tucked into my RAV4 with no cracked windows, no fan running, just my sleeping bag and a CO₂ monitor to keep me honest. The night starts the way a lot of my solo trips do: muddy backroads, hunting for a Crown Land spot, and finally settling in for a cozy, stealthy setup while the weather does its thing. Once I’m parked, I walk you through my little rainy-night routine—reading, relaxing, warming up with apple cider—and then we get into the actual experiment. I explain the difference between carbon monoxide (CO) and carbon dioxide (CO₂), why people mix them up, and what I’m actually measuring overnight. In the morning, I share the readings and the real “gotcha” of sleeping sealed up: condensation. My takeaway is simple: the air-quality fear is usually not what people think it is, but moisture management is very real—especially if you’re trying to stay stealthy, warm, and dry while camping solo.