Whereabouts at the Chengdu airport do we apply for the 144 hour transit permit?

I'm assuming there is a desk or office in the airport somewhere, however when I did the same thing in Guangzhou in 2017, there were no signs to indicate where to go or what the procedure was. It took me 6 hours to leave the airport that day and I don't want to go through the same experience again.

Thanks, Matt