Nonsmoking or Non-smoking [closed]

Would one write that someone is “a nonsmoking so-and-so” or “a non-smoking so-and-so”? I'm not sure if the hyphen is necessary or superfluous.

Style guides differ on this issue of punctuation. The Chicago Manual of Style, fifteenth edition (2003) recommends closing up practically all prefixed words including those beginning with non-:

Hyphenation Guide for Compounds, Combining Forms, and Prefixes

...

3. Words Formed with Prefixes

Compounds formed with prefixes are normally closed, whether they are nouns, verbs, adjectives, or adverbs.

...

[Relevant examples:] non: nonviolent, nonevent, nonnegotiable, but non-beer-drinking

The Associated Press Stylebook (2002) doesn't endorse closing up words that begin with non- as categorically as Chicago does. Nevertheless, nonsmoking appears to fall into its approved group of closed-up spellings:

non- The rules of prefixes apply, but in general no hyphen when forming a compound that does not have special meaning and can be understood if not is used before the base word. Use a hyphen, however, before proper nouns or in awkward combinations, such as non-nuclear.

Words Into Type, third edition (1974) concurs with Chicago and AP:

Prefixes. The modern tendency is to eliminate the hyphen between a prefix and a root unless the root is a proper noun or adjective, such as un-American [cross reference omitted]. ...

[Relevant examples:] nonnative, nonviolent

The guide least inclined to endorse closing up (most) prefixes is The Oxford Style Guide (2006):

5.10.2 Prefixes and combining forms

Words with prefixes are often set as one word, but use a hyphen to avoid confusion or mispronunciation, particularly where there is a collision of vowels or consonants:

[Relevant examples:] non-effective, non-negotiable

The hyphen is used less in US practice. Words beginning with non- and re-, for example, are often set as one word:

[Relevant examples:] noneffective, nonnegotiable

Notice, however, that nonsmoking isn't a spelling that invites confusion or mispronunciation, nor does it involve a collision of consonants in the way that non-negotiable (for example) does. So its entirely possible that Oxford would either approve or tolerate closing up nonsmoking—and the three U.S. style guides unanimously endorse it.

Because hyphenation is ultimately a style issue, you can hyphenate or close up as you prefer, unless you are writing for a publication that specifies a preferred style that you must follow. But in the United States, at least, the strong preference appears to be for nonsmoking, closed up.