11.   It can be blocked by a sheet of paper and cannot penetrate human skin.

12.   It sounded like snapping rubber bands as the laser started to work, creating what looked like little red sparks as it penetrated the skin and dissolved the ink.

13.   Nerve agents penetrate the skin and kill quickly.

14.   Oils that penetrate the skin can get into breast milk.

15.   Pointer lasers, produced by a semiconductor chip, are too weak to penetrate human skin, and feel only slightly warm if focused on a exposed spot.

16.   Small pulsed lasers can also penetrate the skin, but they drill holes which, like needle pricks, can cause pain and take time to heal.

17.   Such devices have wires or tubes that penetrate the skin, increasing the risk of infection.

18.   The chemical penetrates the skin and enters the bloodstream readily.

19.   Theoretically, the bag hits with enough punch to knock down an assailant, but expands to a size that will generally not penetrate the skin.

20.   There is convincing proof that the uranium metal in unexploded weapons presents no danger, the radiation level is low and the rays do not penetrate skin.