Hydrogen, safety informati**

Khaled Hamza · #1 12-29-2010, 09:34 PM

Understanding Hydrogen

Hydrogen is no **** or less dangerous than other flammable materials, including gasoline and natural gas, according to a fact sheet about hydrogen safety ****tly published by the Hydrogen Associati** and the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy. In fact, some of hydrogen’s differences actually provide safety benefits compared with gasoline or other fuels. However, all flammable materials must be handled resp**sibly. Like gasoline and natural gas, hydrogen is flammable and can behave dangerously under specific c**diti**s. N**etheless, hydrogen can be handled safely when simple guidelines are observed and the user has an understanding of its behavior.

Comparis** with Other Flammable Materials

-Hydrogen is lighter than air and diffuses rapidly — 3.8 times faster than natural gas — which means that when released, it dilutes quickly into a n**flammable c**centrati**.
-Hydrogen rises two times faster than helium and six times faster than natural gas at a speed of almost 45 mph (65.6 feet/sec**d). Therefore, unless a roof, a poorly ventilated room, or some other structure c**tains the rising gas, the laws of physics prevent hydrogen from lingering near a leak (or near people using hydrogen-filled equipment). Simply stated, to become a fire hazard, hydrogen must first be c**fined; however, because hydrogen is the lightest element in the universe, it is very difficult to c**fine. Industry takes these properties into account when designing structures in which hydrogen will be used. The designs help hydrogen escape up and away from the user in case of an unexpected release.
-Hydrogen is odorless, colorless, and tasteless, so human senses w**’t detect a leak. However, given hydrogen’s tendency to rise quickly, a hydrogen leak indoors would briefly collect ** the ceiling and eventually move toward the corners. For that and other reas**s, industry often uses hydrogen sensors to help detect hydrogen leaks and has maintained a high safety record using them for decades.

Combusti**

-Hydrogen combusti** primarily produces heat and water. Due to the absence of carb** and the presence of heat-absorbing water vapor created when hydrogen burns, a hydrogen fire has significantly less radiant heat compared with a hydrocarb** fire. Because a hydrogen fire emits low levels of heat near the flame (the flame itself is just as hot), the risk of sec**dary fires is lower.
-Like any flammable substance, hydrogen can combust. But hydrogen’s buoyancy, diffusivity, and small molecular size make it difficult to c**tain and create a combustible situati**. In order for a hydrogen fire to occur, an adequate c**centrati** of Hydrogen, the presence of an igniti** source and the right amount of oxidizer (like oxygen) must be present at the same time.
-Hydrogen has a wide flammability range (4% to 74% in air), and the energy required to ignite hydrogen (0.02 mJ) can be very low. However, at low c**centrati**s (below 10%) the energy required to ignite hydrogen is high — similar to the energy required to ignite natural gas and gasoline in their respective flammability ranges — making hydrogen realistically **** difficult to ignite near its lower flammability limit.

Explosi**

-An explosi** cannot occur in a tank or any c**tained locati** that c**tains **ly hydrogen. An oxidizer such as oxygen must be present in a c**centrati** of at least 10% pure oxygen or 41% air. Hydrogen can be explosive at c**centrati**s of 18.3% to 59%. Although this range is wide, it is important to remember that gasoline can present a greater danger than hydrogen because the potential for explosi** occurs with gasoline at much lower c**centrati**s: 1.1% to 3.3%. Further****, there is very little likelihood that hydrogen will explode in open air due to its tendency to rise quickly. This is the opposite of what we find for heavier gases such as propane or gasoline fumes, which hover near the ground, creating a greater danger for explosi**.

Asphyxiati**

With the excepti** of oxygen, any gas can cause asphyxiati**. In most scenarios, hydrogen’s buoyancy and diffusivity make hydrogen unlikely to be c**fined where asphyxiati** might occur.

Toxicity/Pois**

Hydrogen is n**toxic and n**pois**ous. It will not c**taminate groundwater (it’s a gas under normal atmospheric c**diti**s), nor will a release of hydrogen c**tribute to atmospheric polluti**. Hydrogen does not create "fumes."

bigleve2100 · #2 08-12-2011, 06:05 AM

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