Compressed Gas Cylinder Safety

There are many types of material packaged as compressed gases including atmospheric gases (carbon dioxide, nitrogen, and oxygen), fuel gases (hydrogen), gases used for organic synthesis (phosgene), etc. The hazards associated with the use of these gases range greatly and may include asphyxiation, fire and explosion, adverse health effects cause by toxic material, and physical hazards associated with the failure or rupture of a compressed gas cylinder. To ensure the safety of people and property, users of compressed gas must follow the rules for safe handling and storage outlined below.

In order to promote gas cylinder safety please post Operation Instructions for Regulators & Cylinders near your gas cylinders.

Labeling

Cylinders should be marked with a clear label identifying the contents. No cylinder should be accepted without a proper label.

  1. Color coding is not a reliable way to identify the contents of gas cylinders.
  2. If a label becomes damaged or worn to the point it is illegible, the manufacture or supply should be contacted and asked to remove tank from the premises.
  3. Cylinders which are empty must be marked with the word EMPTY or the lettering MT.

Handling

  1. Wear appropriate Personal Protective Equipment (PPE) when working with compressed gases.
  2. Cylinders should always be transported using gas cylinder hand trucks with appropriate chains or straps to secure the cylinder in place during transport.
  3. Never drop, bang, or strike cylinders against each other nor against solid objects.
  4. Do not use the valve cover to lift a cylinder; they could be damaged and become unattached causing the cylinder to drop on a hard surface possibly resulting in an explosion.
  5. Do not lift a cylinder by its cap; the cap or cylinder could come loose and cause harm.

Storage

  1. Compressed gas cylinders must be stored upright and secured with a chain or strap that is connected to a wall or bench mounted device. In lieu of these devices an approved gas cylinder hand-truck or floor stands may be used to prevent tipping or falling.
  2. Caps used for valve protection must always be securely fastened, unless the cylinder is being used.
  3. Incompatible gases must be segregated by appropriate distance indicated in Table 1 below.
  4. The amount of gas stored in an each occupancy (individual laboratory space) is limited. Table 2 indicates amount of gases that can be kept in laboratories.
  5. Empty gas cylinders should be separated from full or partially full cylinders. These tanks must be marked with the word EMPTY or the lettering MT.
  6. Cylinders should not be exposed to an open flame or to any temperature above 125 degrees Fahrenheit.
  7. Place cylinders in a location where they will not be subject to mechanical or physical damage, heat, or electrical circuits to prevent possible explosion or fire.
  8. Store cylinders in a dry, well-ventilated area away from flames, sparks, or any source of heat or ignition.
  9. Cylinders should not be exposed to continuous dampness, stored near salt or other corrosive chemicals or fumes. Corrosion may damage cylinders and cause their valve protection caps to stick.
Table 1: Separation of Gas Containers, Cylinders, and Tanks by Hazard Class (Source: NFPA Code, §55)
Gas CategoryOther GasUnstable Reactive,
Class 2, 3, or 4
CorrosiveOxidizingFlammablePyrophoricToxic or Highly Toxic
Toxic or Highly toxic6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)
Pyrophoric6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)
Flammable6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)
Oxidizing6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)
Corrosive6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)
Unstable Reactive, Class 2, 3, or 4 6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)
Other Gas6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)6.1 m (20 ft)

Using this Chart: To determine if two gases must be segregated locate one gas category in the far left and then the second gas type in the top row. The distance between the two types of gases will be given where the two cross on the chart. (—) indicates no separation necessary.

Table 2: Maximum Allowable Quantity of Gases per Laboratory (Source: NFPA Code, §55)
Unsprinklered AreasSprinklered Areas
MaterialsNo gas cabinet, gas room, or exhausted enclosureGas cabinet, gas room, or exhausted enclosureNo gas cabinet, gas room, or exhausted enclosureGas cabinet, gas room, or exhausted enclosure
Corrosive Gas
Liquefied
Nonliquefied

68 kg (150 lb)
23 m3 (810 ft3)

136 kg (300 lb)
46 m3 (1620 ft3)

136 kg (300 lb)
46 m3 (1620 ft3)

272 kg (600 lb)
92 m3 (3240 ft3)
Cryogenic Fluid
Liquefied
Nonliquefied

0 L (0 gal)
170 L (45 gal)

170 L (45 gal)
340 L (90 gal)

170 L (45 gal)
340 L (90 gal)

170 L (45 gal)***
681 L (180 gal)
Flammable Gas
Liquefied
Nonliquefied

114 L (30 gal)
28 m3 (1000 ft3)

227 L (150 gal)
28 m3 (2000 ft3)

227 L (60 gal)
28 m3 (2000 ft3)

454 L (120 gal)
56 m3 (4000 ft3)
Highly Toxic Gas
Liquefied
Nonliquefied

0 kg (0 lb)
0 m3 (0 ft3)

2.3 kg (5 lb)
0.6 m3 (20 ft3)

0 kg (0 lb)
0 m3 (0 ft3)

4.5 kg (10 lb)
1.1 m3 (40 ft3)
Nonflammable Gas
Liquefied
Nonliquefied

No Limit
No Limit

No Limit
No Limit

No Limit
No Limit

No Limit
No Limit
Oxidizing Gas
Liquefied
Nonliquefied

57 kg (15 gal)
43 m3 (1500 ft3)

114 kg (30 gal)
85 m3 (3000 ft3)

114 kg (30 gal)
85 m3 (3000 ft3)

227 L (60 gal)
170 m3 (6000 ft3)
Pyrophoric Gas
Liquefied
Nonliquefied

0 kg (0 lb)
0 m3 (0 ft3)

0 kg (0 lb)
0 m3 (0 ft3)

1.8 kg (4 lb)
1.4 m3 (50 ft3)

3.6 kg (8 lb)
2.8 m3 (100 ft3)
Toxic Gas
Liquefied
Nonliquefied

68 kg (150 lb)
23 m3 (810 ft3)

136 kg (300 lb)
46 m3 (1620 ft3)

136 kg (300 lb)
46 m3 (1620 ft3)

272 kg (600 lb)
92 m3 (3240 ft3)

*** Gas cabinet required or exhausted directly outdoors or to exhaust hood.

Regulators, Manifolds, and Valves

The purpose of the regulator is to control the flow of gas and lower the pressure from the cylinder. The regulator not only acts as a control regarding the flow and distribution of gas but also as a safety barrier between the high pressure of the tank and the end use.

  1. Use only the regulator designed for the gas being used. If the regulator is not the correct one, the connector will not fit. Do not force or change connections. Manufacturers and distributors should also be able to identify the valves and associated equipment required for each gas.
  2. Always use a cylinder wrench or other tightly fitting wrench to tighten the regulator nut and tube connections. Use a crescent or open-end type wrench: pipe type wrenches may round the fittings.
  3. Lecture bottles use universal threads and valves, some of which are interchangeable. Label all associated equipment with the gas name to prevent unintentional mixing of incompatible materials.
  4. Valves and regulators should undergo periodic maintenance and repair. A visual inspection should be performed before each usage to detect any damage, cracks, corrosion or other defects. Long term maintenance or replacement periods vary with the types of gases used, the length of use, and conditions of usage. Consult the cylinder, regulator or gas supplier for recommended valve and regulator maintenance schedules.
  5. If the regulator is dropped, it should be sent to the supplier for servicing.
  6. Test regulator for leaks. A soapy water solution can be used for argon, nitrogen, hydrogen or air. For other gases consult supplier.
  7. Do not use teflon tape, which does not seal the connection and could clog the regulator or contaminate the gas stream.
  8. For gasses other than hydrogen: Prior to attaching regulator, crack open the cylinder valve for an instant and close quickly. This will blow out any foreign matter that may be inside the valve port.
    • CAUTION: If the cylinder valve is opened too much, the cylinder may tip over due to the force of escaping gas. Do not stand in from of the valve port.
  9. Open cylinder valves slowly. Point the valve opening away from yourself and other persons. Never use a wrench or hammer to open or close a hand wheel type cylinder valve. If the valve is frozen and cannot be operated by hand, return the cylinder to the vendor.
  10. When removing a regulator from a cylinder, the cylinder valve is closed first, then release the pressure from the regulator.

Some advice for specific gasses:

Visual Inspection

Hydrogen (H2)

Hydrogen is a colorless, odorless, tasteless, highly flammable, and non toxic gas. Due to this high flammability of hydrogen (lower flammable limit of 4% by volume) special safety precautions in addition to the safety precautions mentioned above must be taken:

  1. Hydrogen gas should never be stored near oxygen, chlorine, or other oxidizing gases. These materials must be separated by at least 20 feet or an appropriate gas cylinder cabinet must be used.
  2. Cylinders must be located at least 25 feet from open flames, ordinary electrical equipment, and/or any ignition source.
  3. Hydrogen gas must never be stored below grade, or below the ground of the terrain which surrounds the building.
  4. Labels identifying cylinders as "Hydrogen" must be visible and free of obstructions.
  5. When attaching a regulator or control valve do not partially open, or 'crack', the hydrogen cylinder valve. This may lead to self-ignition of the hydrogen.

Prior to the Case purchasing department completing any order for flammable, corrosive, or toxic gas, EHS must approve the intended location of the gas. The order will only be approved if all the above criteria are met. If you have any questions feel free to contact EHS at 368-2907.


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