Sources of CO Indoors and Associated Health Risks
Even low levels of carbon monoxide can cause problems, especially for people with heart conditions, children, or the elderly. CO exposure often goes unnoticed until symptoms appear—and by then, it could already be dangerous.
| CO Level (ppm) | Effect |
|---|---|
| 1–3 ppm | Normal indoor background |
| 4–8 ppm | May cause mild discomfort with long exposure |
| 9+ ppm | Exceeds EPA 8-hour limit |
| 35+ ppm | Exceeds EPA 1-hour limit; causes headaches and dizziness |
| 100+ ppm | Life-threatening with prolonged exposure |
| 400+ ppm | Medical emergency – immediate danger |