I got a phone call yesterday from one of our mechanics saying that on all the trips we make to CSX, but not anywhere else in China that immigration comes in with a individual carrying a 5 gal unmarked sprayer and sprays unknown substances in the galley and main deck area of the aircraft. It's a non-authorized procedure as I just found out and was curious to know what it could possibly be? I know in China during the first outbreak China was doing this on a massive scale and those chemicals were killing people. Are there anyone else flying air cargo in China have this same weird problem? They use the entire 5 gallons of this substance apparently and our personal is concerned with no one able to give a straight answer.