The important information in this chapter is summarized below.

Compressed Gases Summary

The following terms are defined:

Compressed gas is defined as any material or mixture having m the container an absolute pressure exceeding 40 psi (pounds per square inch) at 70F, or regardless of the pressure at 70F, having an absolute pressure exceeding 140 psi at 130F; or any flammable material having a vapor pressure exceeding 40 psi at 100⁰F.

Compressed Gases Summary (Cont.)

Non-liquified gases are gases that do not liquify in containers at ambient temperatures and under pressures attained in commercially used containers that range to 2000 to 2500 psig.

Liquified gases are gases which do become liquids to a very large extent in containers at ordinary ambient temperatures, and at pressures from 25 to 2500 psig.

Dissolved gases are gases dissolved into a solution.

The major families of gases are:

Atmospheric gases

aerosol gases

fuel gases

poison gases

refrigerant gases

The general safety precautions for gases:

Ensure there is adequate ventilation of enclosed areas.

Avoid entering unventilated areas that might contain high concentrations of gas without first putting on breathing apparatus with a self-contained or hose-line air supply.

Take precautions against skin or eye contact with liquified gases that are toxic or very cold, or both.

The proper storage and handling of containers avoids many possible incidents.

The safety precautions for working with cryogenic liquids are:

Stand clear of boiling or splashing liquid and its vapors.

Never allow an unprotected part of the body to touch uninsulated pipes or vessels that contain cryogenic fluids.

Use tongs, or a similar device, to withdraw objects immersed in a cryogenic liquid.

Use appropriate eye and hand protection.

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.