Compressed Gases Summary (Cont.)

Hazards of Chemicals and Gases DOE-HDBK-1015/2-93 COMPRESSED GASES Rev. 0 CH-05 Page 29 Compressed Gases Summary (Cont.) The physical properties and special precautions for hydrogen include the following: It is the lightest of all elements It cannot be detected by any of the senses It has a flammable range of from 4.1 percent to 74.2 percent by volume in air It burns with an almost invisible flame Hydrogen is classified as an asphyxiant, and special precautions, such as adequate ventilation and the elimination of possible sources of ignition, should be taken to prevent hydrogen accumulation. The physical properties and special precautions for nitrogen include the following: It makes up more than 78 percent of the earth's atmosphere It will not burn or support combustion It cannot be detected by any of the senses It is used to inert systems that contain, or have contained, flammable liquids or gases It is fairly soluble in the blood and if the dissolved nitrogen escapes from the blood in the form of small bubbles in the bloodstream, intense pain occurs and effects are often fatal Nitrogen is an asphyxiant and it could cause a serious oxygen deficiency. Special precautions, such as adequate ventilation, should be taken to prevent nitrogen accumulation. The physical properties and special precautions for oxygen include the following: It supports combustion, but does not burn Ignition temperature of a combustible material is lower in enriched oxygen It readily combines with other elements and compounds, with spontaneous ignition in some cases When oxygen comes in contact with oil, grease, or fuel oils, it may ignite violently. Every possible precaution must be taken to prevent this combination. If pure oxygen were inhaled continuously for extended periods the reactions in the body would be too rapid and cause harmful effects. Finally, oxygen valves should be operated slowly. Abruptly starting and stopping oxygen flow may ignite contaminants in the system.