OC gas (Oleoresin Capsicum) or pepper spray is a great weapon to temporarily disable a suspect without casing permanent damage. Pepper spray is made up of natural ingredients including capsicum (pepper) and oleoresin (resin). Pepper spray effects different people in different ways - some people experience burning skin and eyes, temporary blindness, sensitivity to light and lots of pain .... however other people have a much less severe reaction to it. Watch the video below of man who is sprayed in the face with pepper spray and says to the officer

you're going to need more than that

Seems like this guy is immune to pepper spray and bullets!

During my training to become a police reservist we had a session on pepper spray. This included being sprayed in the face. All the students line up in rows with buckets of water behind us. Each student has two instructors with them, one to spray them in the face with pepper spray, and the second to lead the student to the buckets. The two instructors with me where both Inspectors who had been training us over the past three months. During this time I had really really battled to speak and communicate with these two Inspectors. Trying to form words was tough and I had many blocks when speaking to the Inspectors. My responses where limited to 'yes' 'no' and one or two other forced words. The one Inspector sprayed me in the face (not so bad), and then shouted "open your eyes" which I did (really bad). The second Inspector then lead me to the bucket of water. The crazy thing was that the second I was sprayed I was able to speak 100% fluently to the Inspectors and say whatever I needed to ("more water!").

I guess due to the pain and temporary blindness I wasn't thinking one bit about my speech so was able to speak fluently. This was reassuring as I have had this fear in the back of mind that I will be in an emergency and will not be able to shout 'watch out for that bus' , 'duck' or 'fire' as needed. I know now that in an emergency situation my speech will be the furthest thing from my mind and I will be able to speak.