Swarm

The swarm buzzed along down the street while you hide in an old fridge at the back of an office building. The smell of the rotten contents which had until moments ago been inside threatens to make you vomit but any noise will attract attention so you swallow the bile down. The monitor on your wrist, a boxy thing the size of a large watch, just kept climing as the bulk of the swarm passes. Class2.2 the Class2.3 and up. The louder the swarm gets the closer to Class3 it gets, the point where it becomes intelligent, where a bunch of rotten things on the floor in front of a closed fridge will be like a neon sign pointing to your binding spot.
The sound grows so loud that even covering your ears does little as the fridge vibrates from the buzzing. Class2.5. You hold your breath hoping they will pass, 'please don't go to 3' you say over and over in your head. Little metal legs skitter over the fridge, and your heart freezes.
Class2.4. You want to sigh but know they are just outside. Slowly, excruciatingly slowly, the count ticks down until the sound is gone. The swarm has passed. Pushing the door open you step out with shaking legs. It's the closest you'd come to dying