Nitrogen oxide

Nitrogen oxide is like a very bad smell that comes out of cars and factories. It's made up of two types of gas: nitrogen and oxygen. These gases usually don't bother us, but when they come together in a car engine or a factory, they make this smelly gas.

The smelly gas is not good for us because it can make our lungs hurt and it can even cause problems with our hearts. It's also not good for the environment because it can make plants and animals sick.

But we can make things better by making sure that cars and factories don't make too much of this bad gas. We can use machines and special tools to help clean up the air and make it smell better.