Leonard: What are you doing in there?
Sheldon: I'm making hydrogen sulphide and ammonia gas. Just a little experiment in pest control.
Raj: It's not gonna work, dude. I grew up in India, an entire subcontinent where cows walk in the street, and nobody has ever had a solid bowel movement.
Sheldon: Well, we'll just see how long you can hold out.
Raj: Well, we'll just see how your noxious gas fares against my cinnamon-apple-scented aroma therapy candles.
Leonard: Didn't you say you're making hydrogen sulphide gas?
Sheldon: Yes.
Leonard: Isn't that flammable?
Sheldon: Highly. Oh, dear. [explosion]