The reason why people are wary is not fear of an explosion, but rather
carbon monoxide, and rightfully so. My in-laws' furnace just broke, and it developed a carbon monoxide leak. My mother-in-law couldn't figure out why an alarm in her house was going off when there was no fire or smoke. She called the fire department, and they came out to the house. When she opened the garage doors, enough CO got out of the house that the alarm turned off. She just thought she had a headache. It was a very near miss.