I have a pet peeve about graphs with bad / non-existent labeling. Here is how to read the graph: The black line is the outside air PM2.5. The green-yellow-oran

I have a pet peeve about graphs with bad / non-existent labeling. Here is how to read the graph: The black line is the outside air PM2.5. The green-yellow-orange-red bars are the indoors air PM2.5.