There are several ways to sign this and I'm not overly satisfied with any of them.
So, I'll just show you the "compound" version that combines the ASL signs "second-hand" and "smoke."
SECOND-HAND SMOKE:
Note: A student asked me how to sign that if the person didn't already understand the concept of "second-hand smoke."
I replied by showing the signs: SOMEONE SMOKE HE, OTHER PEOPLE THEY-(sweep) INHALE.
Notes: