CHAPTER 5:

---

A. Compressed Gases in Cylinders 

---

1. Policy

Users of compressed gases shall be familiar with the pertinent equipment and the characteristics of the gases.

2. Responsibilities

1. Supervisor
1. Ensures that JAC policies are enforced and good safe laboratory practices are used.
2. Provides for and requires adequate instruction in the use and maintenance of gas cylinders by all employees handling compressed gases.
   

2. Employee

Performs all work with compressed gases in accordance with JAC policies and good safe laboratory practices.


3. Site Safety Advisor

1. Ensures that JAC policies are enforced and good safe laboratory practices are carried out.
2. Assists, advises and provides training as necessary.

3. General Safe Handling Procedures

1. Compressed gas cylinders must be secured at all times so they cannot fall. Storage on approved hand trucks satisfies this requirement.

2. Cylinders shall never be dropped or permitted to strike each other violently.
   

3. Valve safety covers shall be in place until pressure regulators or needle valves are ready to be attached.

4. The names of the cylinder contents must be permanently attached to the cylinders. Color coding alone is not acceptable. This identification shall not be removed, covered or defaced.

5. Cylinders may be moved on chain equipped hand trucks or carts; they must never be rolled on their sides or dragged.

6. Employees must not attempt to repair cylinders or cylinder valves, or to force stuck or frozen cylinder valves.

7. Before installing a regulator on a compressed gas cylinder, the valve port shall be inspected and cleaned.  The valve may be gently opened to expel any foreign material depending upon the nature of the compressed gas. Stand clear of valve port and face valve port away from personnel. EXCEPTION: DO NOT open cylinder valve on acetylene cylinders before installing a regulator.  Acetylene can ignite by decomposition above 15psig.

8. Compressed gas must not be used to dust off clothing.

9. Cylinders shall not be stored near corrosive chemical or fumes.

10. Where stored in the open, cylinders must be protected from direct sunlight.

11. Oxygen cylinders must be stored at least 20 feet away from those containing any fuel gas.

12. Cylinders must not be lifted by machinery unless they are on a safe stand or cradle or are otherwise positively secured against falling or being dropped.

13. Special arrangements will be made to secure cylinders while they are being transported. Carrying them loosely on the back of a truck or in a pickup is prohibited.

14. Oxygen cylinders will be kept free from oil or grease. Use of oil or grease as a lubricant for oxygen valves or attachments is prohibited.

15. Smoking or flame is prohibited near welding gas and oxygen cylinders or outlets.

16. Do not store or transport acetylene cylinders on their side, as this causes the acetylene to become less stable and unsafe.
    

4. Restricted Products

1. The purchase and use of toxic gases are controlled. The Site Safety Advisor must be notified of intent to work with toxic gases prior to their proposed use to allow time for making necessary safety preparations. Large cylinders of toxic gases shall not be purchased if it is possible to use small cylinders. 

2. Laboratories using toxic gases shall have respirators available that are effective against the agent. Respirators will be issued by the Site Safety Advisor. The Site Safety Advisor will provide training for the proper use of respiratory protective equipment.

5. Acceptance of Cylinders from Vendors

1. The contents of cylinders must be identified with decals, stencils, or other markings on the cylinders. Color codes alone or tags hung around the necks of the cylinders are not acceptable. Cylinders lacking proper identification must not be accepted from the vendors.

2. Cylinders must not be accepted from the vendors unless the valve safety covers are in place and properly tightened.

3. Vendors moving cylinders must use chain equipped hand trucks or carts. Cylinders must not be rolled on their sides or dragged.

6. Handling and Storage of Cylinders without Regulators

1. The valve safety covers must be left on the cylinders until cylinders are secured to walls, benches, or stable pieces of equipment and are required for use.
   

2. Cylinders must be transferred only by approved carts or hand trucks. They must not be rolled on their sides or dragged. The valve safety covers must be in place and the cylinders secured to the carts during transport.

3. Tags marked full, in service or empty will be placed on cylinders of compressed gases.

7. Pressure Regulators and Needle Valves

1. The valve fittings of cylinders used to store different families of gases are different and will allow regulators or needle valves to be attached that are safe for use with those gases. Use of adapters to connect regulators to cylinder valves defeats this safeguard and is not permitted. Only pressure regulators and needle valves approved for the gases may be used.

2. Threads and points of unions must be clean. These surfaces must be inspected before they are connected.

3. When attaching regulators or needle valves, the connections must be tightened firmly. Wrenches of the proper size shall be used. Pliers shall not be used, as they damage the soft brass nuts. Need for excessive force often indicates that the regulators or needle valves do not fit the cylinders. Leaks at the unions between the regulators and the cylinder valves are usually due to damage to the faces of the connections. Attempts to force a tight fit may damage the previously undamaged half of the connection. If the cylinder valve faces are damaged, the cylinders shall be returned to the vendors. Employees shall not attempt to repair them. Damaged regulators shall not be used until repaired by an approved facility.

4. After attaching the pressure regulator to the cylinder, the delivery pressure adjusting screws of the regulators shall be turned out until they turn freely. The cylinder valves shall be opened slowly.  Personnel shall avoid standing directly in front of the regulators at this time as the pressure of the cylinders may blow the glass from the front of a faulty gauge. After the valves are opened, the regulators and fittings shall be checked for leaks. The cylinder valve handles shall be left attached to the valves while the cylinders are in use. Cylinder valves that "stick" and do not open when the usual amount of force is applied may be damaged. Personnel must not attempt to force them open, but shall return these cylinders to the vendors, stating on the cylinders that the valves are stuck.

5. Pressure in full cylinders shall be indicated on the cylinders or labels. Lack of full pressure may indicate leaks at the connections between the cylinders and regulators, damaged regulators, or incompletely filled cylinders. Employees who, on fitting a regulator, discover the pressure is not as expected shall alert their supervisor or the Site Safety Advisor.

6. Employees shall connect delivery lines to the low pressure outlets of the regulator valves or to the needle valves. Where low pressure lines are used, their valves shall be closed and line pressures adjusted by turning the regulator delivery pressure adjusting screws until the desired pressures are shown on the delivery pressure gauges.

8. Cylinder Leaks

1. Unless there are reasons to believe that cylinders are leaking, testing for leaks may be done after the pressure regulators are attached to the cylinder valves and the valves opened. Soapy water painted over the valves and connections will indicate most gas leaks.

2. Compressed gas cylinders are tested for leaks when they are filled; however, leaks have been detected when cylinders were connected in laboratories. Personnel shall not attempt to repair leaks caused by loose valve stem packing. Leaking cylinders of nontoxic, nonflammable gas shall be returned to the vendor. Leaks from cylinders of toxic or flammable gases require immediate attention by competent personnel. Decisions of how to handle the problem will depend on the kind of gas, the size of the leak, the area where the cylinder is located, and other factors. Personnel must wear appropriate protection when attempting to move leaking cylinders of toxic gases. Assistance can be obtained from the Site Safety Advisor.

9. Empty Cylinders

1. A small amount of gas must be left in the cylinders and the cylinder valves must be closed to prevent contamination of the inside of the cylinders.

2. Empty cylinders shall be marked "EMPTY" or "MT".

3. Valve safety covers and the labels showing contents must be in place.

4. Empty cylinders must be secured at all times so they can not fall. Storage on  approved hand trucks satisfies this requirement.

5. Personnel will not remove the cylinders which are not appropriately marked or which do not have protective valve covers in place, and shall report this to their  supervisor.
   

---

B. Cryogenic Liquids 

---

1. Policy

Cryogenic liquids may be used only in a manner that is safe for all JAC employees and visitors and in accordance with the procedures outlined below.

2. Responsibilities

a. Supervisor
1. Ensures that JAC policies are enforced and good safe laboratory practices are used.
2. Provides for and requires adequate instructions and protective equipment for use with cryogenic liquids.

b. Employee
Performs all work with cryogenic liquids in accordance with JAC policies and good safe laboratory practices.

c. Site Safety Advisor
1. Ensures that JAC policies are enforced and good safe laboratory practices are carried out.
2. Assists, advises and provides training as necessary.
3. Provides personal protective equipment and clothing as required.

3. Procedures for Handling Cryogenic Liquids

1. Introduction

Because of the extremely low temperatures of cryogenic liquids and their vapors, direct skin or eye contact can result in severe damage to tissues similar to burn injuries. The most commonly used cryogenic liquids at the JAC are liquid nitrogen which has a temperature of -196^oC (-321^oF) and liquid helium which has a temperature of -269^oC (-452^oF). In general, it shall be remembered that cryogenic liquids are extremely cold and that a small amount of volume of liquid produces a large volume of gas (expansion ratio is approximately 700:1 for both liquids).
 
2. Handling Procedures for Cryogenic Liquids

1. Protective Clothing

1. Suitable protective clothing for the operation in hand shall be used. Protective eyewear with side shields shall always be used and JAC will provide protective goggles (suitable for use by those wearing glasses). Gloves will also be provided and staff who make frequent use of them, or of the goggles, will be provided with a personal pair on request to the Site Safety Advisor.

2. Suggested protective clothing may consist of, depending on hazard, rubber aprons, overalls without pockets or cuffs, and hightop shoes to protect against skin contact in the event of a splash or spill. Cuffless trousers shall be worn outside boots or over the shoes to shed spilled liquid.

Transfer of unused liquid nitrogen in hand held dewar.

The unused liquid nitrogen can be poured back into the larger storage dewars from the hand held dewar providing the unused liquid nitrogen is not contaminated.

3. Transfer of liquid nitrogen into lab 20 dewars.

1. Unattended transferring of liquid nitrogen is prohibited.

2. If liquid nitrogen overflows onto the extension of the lab 20 dewar, a warning sign must be posted to inform staff to use gloves before handling the dewar.
   

3. Ventilation

Cryogenic liquids shall be stored and handled in well ventilated areas to prevent excessive buildup of gas which may cause asphyxiation.

4. Keep Exterior Surfaces Clean To Prevent Combustion

Air will condense on exposed liquid helium cooled surfaces, such as vaporizers and piping. Nitrogen, having a lower boiling point than oxygen, will evaporate first from condensed air, leaving an oxygen-enriched liquid. To prevent the possible ignition of grease, oil, or other combustible materials which could come into contact with the air-condensing surfaces, such areas must be cleaned to oxygen-clean standards. Care must be exercised in disposing of the final residue of an open container of liquid nitrogen since it may be oxygen rich.

5. Keep Air and Other Gases Away From Liquid Helium

The low temperature of liquid helium can solidify any other gas. Solidified gases and liquids allowed to form and collect can plug pressure-relief passages and foul relief valves. Plugged passages are hazardous because of the continual need to relieve excess pressure produced as heat leaks into the continually evaporating liquid. Therefore, always store and handle liquid helium under positive pressure and in closed systems to prevent the infiltration and solidification of air or other gases.  


6. Emergency/First Aid Procedures for Cryogenic Liquids

See Chapter 2 section G for emergency response.

---

C. Glass Vacuum Equipment 

---

1. Policy and Purpose

2. Responsibilities

a. Supervisor
Ensures personnel are correctly trained and are provided necessary safety equipment.

b. Employee
Uses good safe laboratory practices and follows JAC procedures to ensure all vacuum equipment used is securely and adequately taped or shielded.

c. Site Safety Advisor
Ensures that JAC policies are enforced and good safe laboratory practices are carried out.

3. Procedures

1. Use metal or taped vacuum flasks and dewars.

2. Always wear safety glasses with side shields or goggles.

3. When using glass vacuum containers including vacuum desiccators, take one of the following precautions:

1.  Tape the flask with electrical, duct or adhesive tape, or a similar product.

2. Put the flask in a metal container tall enough to hold the entire flask.
3. If the above precautions are not possible, place an approved safety shield between the flask and personnel. Safety shields are fairly effective if the flask is in a fume hood, or similar isolated position, but they are not satisfactory on an open bench.

---

D. Vacuum Pump Exhaust 

---

Exhaust shall be plumbed outdoors or the pump's outlet shall have a mist filter attached.