A woman is urging drivers to think twice before sitting in idling vehicles this winter, sharing a story about the dangers of carbon monoxide poisoning. Can Carbon Monoxide Poisoning Really Occur Outdoors? Carbon monoxide is often called the "silent killer" because it’s colorless and odorless, making it impossible to detect without specialized equipment. Many commenters highlighted the factors that increase the risk of carbon monoxide poisoning. Andrist’s timely seasonal warning reminds us that carbon monoxide poisoning can occur in situations that many drivers consider safe.