You forgot that they don't wake up from sound. When you open that door, hundreds of threads of spider webs would've been simultaneously pulled off, alerting almost every spider inside. And when you head in, you won't feel the minute resistance, but thousands more threads would've caught your hair, forming countless secure anchors from the ceiling to your hair.

If yet still you decide to take a seat, Special Forces of the Spider nation will rappel down from the starting end of those connected threads, and they will strike at your most vulnerable - mid-clench and when your legs are pins and needles, so that even the ground troops could join in on a pincer move at you.

Even if you leave, at least half of the spiders would still hang on to the threads going back to your hair, so that for the coming hours, you would feel like having invisible hair on your face, ears and neck, for the top of your head has become their new nest.

Nuke it from orbit. It's the only way to be sure.