For decades, carbon monoxide (CO) safety education has relied on a familiar visual: a chart linking parts per million (PPM) to predicted health effects. It’s neat, it’s easy to reference, and it’s dangerously incomplete. Because carbon monoxide exposure doesn’t follow charts. It follows conditions: who you are, where you are, and how long you’re there. That’s why it’s time for a new way to understand CO’s impact: a model that puts people, not numbers, at the center.