Can you fail a pee test for pot due to secondhand smoke? I haven't smoked in years, but my housemate does several bong hits a day, and some smoke must wind up in my lungs. I'm a substitute teacher hoping to go full-time, and I'm afraid I'll get an offer only to flunk the drug test and get blacklisted.

—Hip-but-worried teacher

You've got nothing to worry about, Teach, for a couple of reasons. Relax and fire up a bowl while I lay them on you.

First, incidental exposure to pot smoke won't make you fail a drug test unless you're going for a job with a total zero-tolerance policy, like Olympic athlete or skipper of the Exxon Valdez. Most pre-employment drug screens permit up to 50 nanograms per milliliter of weed-related goop in your urine in order to avoid precisely the sort of false positive you're worried about. Unless you've been locked in a windowless van with five snowboarders for a week, your passive ganja-sparking won't get you anywhere near that level.

Second, where are you applying for this teaching job? If it's with Portland Public Schools, chill—it's well-known that most PPS teachers spend half their workday locked in the faculty lounge with a wet towel shoved under the door.

OK, maybe that's not strictly true. But if teachers want to fire up the odd doobie on their own time (and God knows I wouldn't blame them if they did), they'll probably live to brag about it.

"We do an extensive background check of all employees," says PPS spokeswoman Sarah Carlin Ames, "[but] we do not conduct pre-employment drug screening of teachers, nor random tests."

The district does, however, do drug screening on drivers, whose sobriety is arguably more crucial than that of teachers—and whose union, entirely coincidentally, is not as powerful.