It's bleach. It breaks down the chemical bonds in organic compounds. A grass stain is turned to dust so it can be flushed away. It's also an oxidant as there is plenty of O2 about to join the reaction.
Question is, what's the exhaust made of? Stainless that is unreactive (like a sink) or some sort of monkey metal that's already gathering up oxygen molecules and doesn't need encouragement.
Andy
