Corridor Pressure Tap

The hollow ping from that umbrella stand gave me the baseline, but the front door threshold was leaking real data. I marched across the wood floor right to the rubber weatherstrip at the bottom of the heavy apartment door. A tiny draft was whistling in from the building corridor. Next to the door jamb, I found a discarded clear plastic bread clip and a dried grain of uncooked rice on the molding. I jammed the clip flat under the rubber flap, then balanced the rice grain squarely on the exposed plastic tab. Every time the heavy fire door slammed down the hall, the pressure spike buckled the flap, causing the clip to pop and launch the rice grain an inch into the air. A binary seismic trigger out of kitchen trash. Works every time.