An odorizer is like a special machine that helps us tell if there might be something dangerous around us that we can't see.
You know how sometimes things that can hurt you, like gas, don't have a smell that we can easily notice? An odorizer adds a smell to those things so that we can tell if they're there and we can be safe.
It's kind of like how your mom might add extra warning labels to things around your house that could be dangerous, like "hot" on a stove or "fragile" on a glass vase. The odorizer is like the "smell" warning that helps keep us safe.