1. Gas Analysis for the Recreational and Technical Diver
Joel D. Silverstein
R.W. Bill Hamilton, PhD

2. OVERVIEW
This workshop is an introduction to preparing oxygen enriched air.
A Blending Technician should be certified to dive with the gas they intend to prepare.
An Oxygen Service Technician should be certified by the manufacture to repair the scuba equipment they intend to convert to oxygen service.
Initialy work with another technican until you feel comfortable working on your own.

3. EQUIPMENT LABELS
Install a tank decal or wrap to identify the particular gas mixture; nitrox, trimix or O2.
Install a contents-tag identifying the FO2 MOD, analysis date, fill pressure, and the analyzers/users initials.
Use appropriate labeling for dedicated scuba regulators and gauges.

4. Identifying Enriched Air Cylinders
4 inch green band on yellow tank
NITROX or Enriched Air stenciled in 2 inch high letters
Non-yellow cylinders have an additional 1 inch yellow band above and below the green

5. Other identification labels
Oxygen Service label
designates cleanliness
annually or if contaminated
Visual Inspection
annually or sooner
Cylinder Contents
identifies contents

6. ENRICHED-AIR SYSTEMS GAVIMETRIC METHOD
Gavimetric mixing requires a sensitive scale that displays weight in 1/4 ounce increments up to 150 lbs.
Eliminates mix variability from temperature and compressibility factors.
Must know the volume of gas at ambient pressure for service rating of the cylinder.
Scale and setup is expensive.

7. O2 ANALYSIS
Analyze the cylinder contents before discharging it to the customer.
Calibrate an analyzer to 100% O2 when the unit is new or the fuel cell is weak.
Before analyzing gas, let the sensor equilibrate to ambient temperature and calibrate to dry air.
Adjust flow rate to specifications and do not block the exit side of the flow tube.

8. Performing Gas Analysis overview
Oxygen analyzers
The need for calibration
Need two analyzers ?
Acceptable range
Analyzing Gas
Flow rate
Calibration
Analyzing the enriched air cylinder

9. Oxygen Analyzers Digital Analog 0.1% accuracy is desirable
Electrochemical oxygen sensor
has limited life span

10. The Need for Calibration
Some units need a flow meter to be accurate
Sets analyzer at a known value (air)
Allows for adjustment of sensor deterioration
Affected by flow rate
Better to calibrate one well than to use two
Air calibrates at 20.9%
Calibrate on 100% when readings fluctuate

11. Analyzing the Gas Flow Rate Acceptable range affects reading
the greater the pressure against the sensor the higher the value shown
1-2 Lpm for one minute
calibrated at same flow
Acceptable range
desired mix +/- 1%

12. The Nitrox Cylinder Calibrate analyzer Analyze cylinder
some auto calibrate
Analyze cylinder
Check for accuracy
If not right
recalibrate
have gas re-mixed
Write information
contents label or tag

13. Contents Label and Fill Log
Write on label
Use permanent marker
Fill date
Oxygen %
PSI (pressure)
MOD
Filled by
Analyzed by
User’s name
Name
Certification number
Date
Fill pressure
Oxygen percentage
Maximum depth limit
Cylinder serial number
Signature