Gas Therapy
I Medical, Laboratory, and Therapeutic Gases and Mixtures
H Oxygen/nitrogen (21% O2/79% N2)
I Oxygen/carbon dioxide (90% to 98% O2/2% to 10% CO2)
IV Gases That Support Combustion
A Cylinder types and composition
1. Type 3AA: Seamless, high-quality, heat-treated tempered alloy-steel
2. Type 3A: Seamless, low carbon, heat-treated steel (no longer produced)
B Cylinder markings: Markings are located at the neck of the cylinder in two groupings (Figure 33-1).
a. Line 1: ICC or DOT, 3A or 3AA, 2015
(1) ICC or DOT: The organization governing the transport of cylinders
(a) ICC: Interstate Commerce Commission. The agency that regulated construction, transport, and testing of compressed gas cylinders from 1948 to 1970.
(b) DOT: Department of Transportation. The federal agency responsible for construction, transport, and testing of compressed gas cylinders since 1970.
(3) 2015: Maximum working pressure in pounds per square inch (psi), which normally can be exceeded by 10% (2200 psi).
1. Large cylinders using hexagonal nut connections (see Section VII, B, American Standard Compressed Gas Cylinder Valve Outlet and Inlet Connections Safety System index)
a. H or K: 9-in. diameter, 55-in. height
b. G: 8.5-in. diameter, 55-in. height
2. Small cylinders using yoke connections (see Section VII, A, Pin-Index Safety System)
D Cylinder capacities for oxygen
E Maximum filling pressure of 3AA oxygen cylinders: 2015 psi plus 10% (2200 psi)
F Calculation of duration of flow from oxygen and compressed air cylinders
1. One cubic foot of gas = 28.3 L
2. The volume of gas in liters in a full cylinder = cubic foot volume × 28.3 L/ft3
3. Dividing the aforementioned determined value by the maximum filling pressure of 2200 psi results in the calculation of a factor indicating the number of L/psi:
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5. L/psi factors for oxygen cylinders
6. Calculation of duration of flow in minutes
a. Gauge pressure multiplied by duration of flow factor (L/psi) equals the number of liters in the cylinder.
b. Dividing the result of no. 6a by the flow in L/min results in the time in minutes that the cylinder will last:
(2)| Gauge pressure | 1500 psi |
| Duration of flow factor | 0.28 L/psi |
| Flow in L/min | 10 L/min |
The cylinder will deliver 10 L/min for 42 minutes before it is completely empty.
d. Clinically it is advisable to subtract 500 psi from the gauge pressure to provide a safety margin before the duration of flow is calculated.
G Color code for E cylinders (Color coding is mandatory for E-sized cylinders only; other sizes of cylinders are not required to follow any coding system.)
1. Oxygen: Green (universal code: white)
7. Oxygen and carbon dioxide: Green and gray
8. Oxygen and helium: Green and brown
10. Nitrogen and oxygen: Black and green (other than room air)
H Hydrostatic testing of cylinders
1. Perform periodic high-pressure testing of gas cylinder integrity.
2. Cylinder expansion is determined by measuring water displacement of an empty cylinder compared with that cylinder when filled to 5/3 of its maximum pressure.
3. All cylinders must be retested every 5 to 10 years, depending on elastic expansion of the original testing.
I Cylinder stem pop-off valves
1. Large cylinders use a frangible disk designed to rupture at a pressure within 5% of cylinder-bursting pressure.
2. Small cylinders use a fusible plug designed to melt at a temperature of 65.6° C to 76.7° C (150° F to 170° F).
J Gas cylinder storage and handling
