Hyphens, En Dashes, Em Dashes

Q. According to CMOS table 6.1 (14th ed.), a noun plus a participle would have a hyphen, and the prefix “non” is a closed compound. So, my question is how would you hyphenate the word “nonlife-threatening” or would you avoid such a word altogether? Thanks.

A. I would use two hyphens (non-life-threatening), both in the spirit of CMOS 6.80 and because “nonlife-threatening” connotes the “threat of nonlife” (i.e., death), which is the opposite of the intended meaning. In general we aim to use hyphens to promote clarity, and we don’t stand on the rules if confusion results.