A polite message just under the tear-off strip says "Please protect your environment, use this bag only when appropriate". So make sure you
really, really want to puke before tearing open the bag.
It might be more honest if it said, "Don't fill up Hong Kong's
scarce landfill space by using this bag, and help boost our corporate
profits by leaving it for the next passenger who sits in this
Thanks to (2000) Bedford McIntosh