Burning unleaded gas inside the four-season tent led to far-and-away the most carbon monoxide. Burning white gas inside the three-season shelter produced the least.
But in just 20 minutes, even the “cleaner” white gas raised levels of carbon monoxide inside the four-season tent above the 150 parts-per-million limit that occupational safety groups say workers shouldn’t be exposed to for more than 15 minutes.
Inside the breezier three-season tents, CO levels stayed under 100 ppm with both types of fuel. “But that was just a 20-minute test,” Betten says. “If you fired it up for an hour or two — or fell asleep — it’s tough to say what would happen.”