On a summer morning last year, Fred Schaub drove his Toyota RAV4 into the garage attached to his Florida home and went into the house with the wireless key fob, evidently believing the car was shut off. Twenty-nine hours later, he was found dead, overcome with carbon monoxide that flooded his home while he slept. “After 75 years of driving, my father thought that when he took the key with him when he left the car, the car would be off,” said Mr. Schaub’s son Doug. Mr. Schaub is among more than two dozen people killed by carbon monoxide nationwide...