Self protection is a habit of mind and nothing will protect you if you are not alert and aware of your surroundings. Protective devices or less lethal weapons come in many forms and I will only mention a few here as it is past my bedtime already. CN is alphachloroacetophenone or Tear Gas as many would call it. It's used in California a lot but many police departments don't use it anymore for a variety of reasons. It is fairly effective if sprayed in a normal person's throat, ear or directly in eyes.
Toxicity can be a problem.
It is called CS after the names of the two British chemists who invented it in the late 1920's. It is measured by percentage but that means nothing in and of itself. Some peppers are hotter than others as we have all noted at restaurants. The Scovel taste scale runs from about 500,000 to a couple of million. Sprays work best on people who are surprised by it.