Sandra Tsing Loh arrives on the trash- and survivalist-gear-strewn stage of the AFI Theater for her one-woman show, I Worry, protected from external threats by a chemical suit and from internal doubts by sarcasm. Her stage vehicle is essentially a stand-up routine writ large (and long, at 85 minutes) that is being presented with theatrical trappings in Woolly Mammoth’s world premiere. In addition to that almost entirely unnecessary detritus-filled setting, there’s modestly atmospheric lighting (to which Loh calls attention at one point by asking the tech staff for something more soothing), sound design (ditto), and a program bio that promises two intermissions (a joke, thank goodness). The evening begins as a blithering full-bore rant about causes of insecurity in an age of war (duct-tape jests) and traffic (SUV jests). Then it segues into an audience-interactive segment in which Loh ventures offstage to give the crowd a reason to worry right along with her. (On press night, she tossed critics’ notepads around the auditorium and lap-danced with the Washington Post’s Peter Marks.) And finally, it ends with the reading of a pair of letters dealing with the fear of death. The first, says Loh, shortly after locating a box that she identifies as holding her mother’s ashes, was written to her and her siblings when their mom had presentiments of doom while facing a long plane trip some 15 years before she died. It is eloquently plain-spoken and graceful, even with the asides Loh uses to prompt laughs. The second letter—delivered in an extended screech that pretty much erases any goodwill engendered by the first—is a substantially more raucous, panic-stricken missive Loh imagines writing to her own children. Understatement, as you may be gathering from this précis, is not the performer’s long suit. She is, however, a reasonably deft crafter of punch lines, albeit ones that rarely tell us things we didn’t already know about ourselves and our fears. David Schweizer’s staging sends her staggering through piles of onstage junk and involves her in occasional audience-acknowledging bits of business. At one point, she harasses the crowd into kicking off its shoes, a gesture that will doubtless prove more ingratiating during warm-weather runs in California than it did at the chilly D.C. premiere. —Bob Mondello