A viral video is warning people about a dangerous winter habit that many drivers think is safe. The video shares a sad story where a daughter died from carbon monoxide poisoning after she and her mother took a nap in an idling car. Carbon monoxide danger exists even in open spacesCarbon monoxide is often called the “silent killer” because it has no color and no smell. While most people know running a car in a closed garage is dangerous, fewer people know that carbon monoxide poisoning can happen even in open areas. More than 400 Americans die from accidental carbon monoxide poisoning every year, not counting fire-related deaths, and over 100,000 people visit emergency rooms for related problems each year.