Many people have a natural fear of chemicals that catch fire easily. In fact, the majority of us fear to enter in a lab where there are a majority of chemicals.
Flash Points Chemicals
Chemicals that are flammable will usually have a low flash point. What is this low flash point? It's the temperature at which the chemical will give out fumes sufficiently enough to catch fire when a lighted flame is brought near to it.
This means that a chemical having a lower flash point than room temperature will give out fumes capable of catching fire even though it is stored at normal room temperatures.
Thus, gasoline with flash point of -20 degree Centigrade will already be able to catch fire at normal room temperature if a light flame is present, while kerosene with flash point of 38 degree Centigrade will not burn when it is kept at a room temperature of 30 degree Centigrade.
Well, that's not totally correct either. In order to burn, three things must be present at the same time: fuel, oxygen and heat. When we talk about flash point, we are talking about the heat to generate sufficient gaseous fumes that can burn, but the chemical will not burn until a higher temperature is reached. That temperature is the ignition point.
The ignition point can be reached if a lighted flame is brought near to the combustible fumes, or it can be from a sparking electrical contact or even from sparks produced from mechanical impact. Very often, it can even come from sparks generated by static electricity.
Even when all these conditions have been reached, fire will not start if there is not sufficient oxygen to support the combustion. This is a very important factor to consider especially when storing flammable chemicals.
Inert Gas Systems
On tanker ships, whenever crude oil or other flammable oil is pumped out, the space occupied by the oil must be replaced, otherwise, there will be a vacuum formed in the tank. This makes it impossible to pump the oil out further. To avoid atmospheric air from being sucked into the tank and creating an explosive mixture, inert gas is led into the tank at a slightly higher pressure than atmospheric.
This inert gas, containing mostly carbon dioxide and nitrogen, is generated from the burning of fuel in the steam boilers. This inert gas is pumped into the tank by means of blowers. The oxygen content in the exhaust gas must always be monitored. Usually it is around 5% and does not support combustion. To prevent corrosion and contamination of the oil, the exhaust gas is cleaned by passing them through a scrubber system. In this case, even though the tank may be nearly empty, the atmosphere above the chemical does not contain oxygen and there is no explosive mixture.
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