The first cigarette inspector Keller is smoking is not only smokeless but it has ash hanging off of it. The inspector is talking with the cigarette in his mouth and despite this fact, the fragile ash hasn't fallen off.
When Mr. Bentley is "cooking" the kippers, the gas stove isn't turned on but the sound of sizzling is still heard.
Inspector Keller throws his cigarette butt into the Jefferson's kitchen sink, which is kind of rude.