How identify the plastic packaging bag toxic?

The first type: water testing method: put the plastic packaging bag into the water, non-toxic plastic bag can be floated into the water after being put into the water; however, the toxic plastic bag is the opposite and will not float to the surface.

The second: hand touch detection method: touch the plastic packaging bag by hand, there is a sense of lubrication non-toxic; otherwise toxic.

The third kind: Jitter detection method: Hold one end of the plastic packaging bag by hand, pat it hard and make a crisp sound, then it is non-toxic; otherwise it is toxic

The fourth: fire detection method: You can cut the plastic packaging bag to one side, with fire, toxic and not easy to burn; toxic and easy to burn, and a pungent odor.

The above is whether food vacuum plastic bag has any harm in the end, and how to identify whether the plastic bag is toxic.