7c. Dry Ice Bombs
Dry ice bombs are devices that use pressure to burst a container, producing a loud report and limited shock effects. No chemical reaction is involved - the container, usually a plastic 2-litre soft drink bottle, is burst by the physical reaction of solid carbon dioxide, CO2, subliming into gas. As the CO2 sublimes, the pressure builds up and eventually the container ruptures. The method is very simple - some dry ice is added to the container, some water is added (about 1/3-1/4 full) and the cap is screwed on tight. Within a short time the container will burst, usually extremely loudly. The water can be omitted if a longer delay time is required. It is reported that these devices can be manufactured using liquid nitrogen instead of dry ice, and no water. This is not recommended as the delay time will be substantially shorter. Safety aspects: Device: NEVER use glass or metal containers! I cannot stress this enough. Dry ice bombs are extremely unpredictable as to when they will go off, and a glass or metal container is very very dangerous to both the constructor and anyone else in the vicinity. Plastic bottles are much safer because the fragments slow down quicker, and thus have a smaller danger radius around the device. Plastic fragments are still very nasty though - don't treat the device with any less caution just because it is made of plastic. There is no way to tell how long you have until the dry ice bomb explodes - it can be anywhere from a few seconds to half an hour. Never add the water or screw the cap on the container until you are at the site you want to use it and you are ready to get away. Never go near a dry ice bomb after it has been capped. If a dry ice bomb fails to go off, puncture it from long range with a slingshot, BB gun, by throwing stones at it or similar. Some indication of timing can be achieved by semi-crushing the container before capping - once the container has expanded back to its original shape it is no longer safe to be anywhere near. Don't forget that the temperature of the day and the size of the dry ice pieces will affect the delay length - don't assume that delay times will be similar between bombs. A hotter day or smaller pieces of dry ice (i.e. greater surface area) will create a shorter delay. Remember, even though no chemical reaction occurs you can still be legally charged with constructing a bomb. Dry Ice: Humans will suffocate in an atmosphere with a carbon dioxide concentration of 10% or more. Use in a well-ventilated area. Dry ice typically has a temperature of about -75 degrees C, so do not allow it to come into contact with the skin, as freezer burns and frostbite will occur. Always use gloves or tongs when handling dry ice.
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