Restaurants here are closed at the drop of a hat. Every restaurant displays a rating code at the door. "A", "B", and "C" are "this place is safe" ratings, below that it's numerical. I've never seen a numerical and seldom see "C" (a rating that's difficult to survive).

Inspections are unscheduled, and if a problem is found the customers already served may finish their meal, but otherwise the place is closed until further notice. It's fun to read the monthly closings in the paper (generally well over 100 of them) where you'll see plenty of names you recognize. Most common is hot water temperature, though a few cockroaches will shut you for "vermin infestation" as will a rodent. Among restaurants with Oriental and Mexican names the most common is "no health permit", in other words "Opened Without Papers".

Most closings are cleard same day or next day when the problem has been fixed and reinspected, but you get a "B" or "C" rating it's going to be up there for awhile because that's considered systemic.