So, have you ever looked outside and seen how the air looks kind of smoggy or cloudy on some days? That's because sometimes there are things in the air that are not very good for us to breathe in.
There are groups of people who study these things and try to figure out how bad the air is and where it might be worse than other places. They use special computer programs and other tools to create pictures of what the air might look like in different places depending on things like how many cars and factories there are around.
They can also figure out if there are certain times of year when the air might be worse, like when there are a lot of wildfires or when it's really hot outside. This helps the government make rules and regulations to try to make the air cleaner and healthier for everyone to breathe. So, these people are like detectives who try to solve the mystery of why the air is not always clean and how we can make it better!