His interest in the biological effects of ionized air was spurred in 1932 when he noticed that the moods of one of his colleagues at Rocky Point Laboratory swung in response to the ions being generated by their equipment. He noted that when the equipment generated negative ions, his colleague's mood was upbeat. Conversely, positive ions generated a downbeat mood. Hansell researched the therapeutic possibilities of negative ions throughout his life. Current scientific studies support his findings, and negative ion therapy may be useful in alleviating depression in some people.