Safety first
Make sure your body is away from the area with cutiing blade
Safety
Stay away from a work area that has cutting tools and that you have no reason for touching. Like this Tool, you don't want to be up close to this tool because it could back fire and cut you or the person that is using it.
Chainsaw
You do not want to be standing in front of someone with this in there hand and they loose control of it and it hurts one of you so its always important to be safe.
Black Knife
Again, you don't want to be with someone that has a knife and they are playing with it like waving it in the air or acting like they are going to throw it and it slips and cuts you or really hurt you. So therefore you must have safety rules to any kind of tool like this.
Concrete Cutter
Stay away from this. It could loose control and cut your foot, ankle, or even your fingers. You have to read the safety book for this machine if you are not sure how to use it. It all goes back to SAFETY RULES.