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The Oxigraf O2iM is the next generation oxygen deficiency (or oxygen enrichment) monitor. Laser diode absorption spectroscopy assures stable, long-life oxygen measurement: there are no electrochemical cells to replace or paramagnetic sensors to recalibrate. The laser diode, derived from high reliability telecommunications VCSEL (vertical cavity surface emitting laser) diode technology, is rated for more than 100,000 hours mean time to failure. The laser diode is thermally and electronically tuned to measure the absorption of oxygen at 763 nm, and also periodically measures the background to provide an automated zero. Pressure and temperature corrections are made to yield the correct oxygen concentration as the weather changes.

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The Oxigraf technology has no moving parts, in contrast to paramagnetic technology. Laser diode technology will have no false alarms due to equipment vibration, mechanical accidents, or even earthquakes. Your oxygen deficiency detector should be as stable as a rock.

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You shouldn't have to worry about a potential oxygen deficiency hazard in your facility any more. Blackout from lack of oxygen will cause a fall and possibly more serious consequences. Oxygen deficiency needs to be annunciated before the first breath. The Oxigraf Safety Monitor responds in less than a second. The transit time of the gas sample through the sampling tube may be 1 second per meter of sampling tube. To respond within 5 seconds, an oxygen alarm monitor with a 1 second response time would need to be placed within 4 meters of the potential hazard. Electrochemical sensors may incorporate long averaging times, 20 or more seconds, for large, abrupt changes in oxygen concentration. Laser diode technology offers short response times to meet your safety requirements.

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Auto Calibration is now standard for the absolute highest accuracy and the ultimate in ease of maintenance of your Oxigraf oxygen deficiency monitor. Connect to a cylinder of calibration gas or run tubing to a space where ambient air is known. Set the calibration interval to your specifications, and you will never need to worry about routine calibration maintenance.

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You don't need a false oxygen alarm situation. It is important that the oxygen concentration measurement be correct irrespective of the foreign gas. Some electrochemical sensors have been found to be inaccurate when helium gas dilutes the oxygen, where a helium spill is the hazard to be detected. The false positive reading was about 3%, the electrochemical sensor reading 19.5% for an actual concentration of 16.6%. The Oxigraf sensor is accurate to ±0.2% with admixtures of noble gases, hydrocarbons, fluorocarbons, CO2, and N2O among other gases tested.

The following paragraph is the abstract of a DOE paper on the subject. An Oxigraf Model O2 analyzer for was used as the reference standard for the test to evaluate various ODM units that were in use at the time by DOE facilities. This was just prior to the introduction of the Oxigraf Model O2iM, so a laboratory version was used for the testing.

Investigation of personal and fixed head Oxygen Deficiency Hazard Monitor performance for Helium Gas.

On May 14, 2001, the Thomas Jefferson National Accelerator Facility (JLAB) conducted a planned liquid helium release into its accelerator tunnel to study the effectiveness of the JLAB facility to vent the helium and therefore limit the oxygen deficiency hazard (ODH). During the test, it was discovered that a wide range of various oxygen deficiency monitors, of different manufacturers, were providing substantial conflicting measurements of the true oxygen level where health effects are of concern. Yet, when tested separately with nitrogen gas as the diluting gas into air, the same models performed very well. This problem, which is associated with helium displacement of air, was found for both personal oxygen monitors and fixed installation monitors from many different manufacturers. By informing other facilities of its findings, JLAB became aware this problem also exists among other national laboratories and facilities. Many manufacturers do not have data on the effects of helium displacing air for their devices. Some manufacturers have now duplicated the test results conducted at JLAB. Since both fixed installation and personal oxygen monitors have become standard safety device in many research facilities and industries in the United States and abroad, it is important that these facilities are aware of the problem and how it is being addressed at JLAB. This paper discusses the methods, procedures and materials used by JLAB to qualify its ODH sensors for helium. Data and graphs of JLAB's findings are provided.

You may find a summary of the above study published by the Brookhaven National Laboratory at lessons learned: Oxygen Monitoring System did not recognize a potentially hazardous situation for information on the publisher, visit the website of the Brookhaven SBMS office.

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The Oxigraf O2iM fixed position oxygen depletion monitor includes a sampling pump, hydrophobic filter, and flow sensor. The microprocessor controller maintains the flow at a constant value. Any flow blockage or pump failure is reported as a low flow fault. Filter impedance can also be measured to indicate a need for filter maintenance. Thus remote monitoring of the flow system is enabled.

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Now optional on the O2iM safety monitor is multiport sampling. Up to four (4) sample locations can be monitored by a single O2iM unit through an internal sample port multiplexer. The O2iM will automatically sample and switch sample input ports and internal valves and fittings are added to the standard housing equipped with the 5-relay board option which contains the required circuitry for this feature.

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An error budget must be established for oxygen safety monitors. Humidity changes can cause a large variation in the oxygen measurement. A hot, wet day relative humidity of 50% at 37ºC (99ºF) corresponds to an absolute humidity of 3.2%. Such a water vapor dilution would cause a variation from the cold, dry air oxygen concentration of 20.9 to 20.2%, a change of 0.7%. If 19.5% is to be the alarm value, then variations from all other sources must be substantially less than 0.7% (the difference between 19.5 and 20.2%).

Therefore, temperature and pressure corrections are important. An oxygen sensor which measures oxygen partial pressure instead of concentration would report an oxygen variation of 2% with a 10% variation in barometric pressure. The Oxigraf sensor is corrected to within ±0.2% over pressure changes of 50% and temperature changes from 0 to 50ºC.

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Your safety is assured when you have both local and remote indication of oxygen deficiency. Oxigraf offers advanced communication capabilities with the Safety Monitor giving you options in setting up your oxygen alarm system.

• RS-232 & RS-485 (Modbus) communication on our Enhanced Relay Board option
• Sealed Box multi-channel status indicator.
• Hazardous Area LED multi-color status indicator.
• Control Room LED multi-light status indicator.
• Rack-Mount LED multi-light status indicator.

Two-way communication gives both remote monitoring and control. A central computer system can monitor every oxygen monitor in your facility for oxygen concentration, alarms, flow and system status. The central system can also control passwords, set alarm levels and initialize each monitor independently. Another advantage of a central control is what we call "remote maintenance". A major cost of oxygen deficiency monitors is the requirement for periodic maintenance and recalibration. With remote maintenance, site service and recalibration are no longer required to be periodic. Any system, power, flow or measurement faults will be flagged on a remote display, and service can be performed on an as-needed basis.

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Two-way communication gives both remote monitoring and control. A central computer system can monitor every oxygen monitor in your facility for oxygen concentration, alarms, flow and system status. The central system can also control passwords, set alarm levels and initialize each monitor independently. Another advantage of a central control is what we call "remote maintenance". A major cost of oxygen deficiency monitors is the requirement for periodic maintenance and recalibration. With remote maintenance, site service and recalibration are no longer required to be periodic. Any system, power, flow or measurement faults will be flagged on a remote display, and service can be performed on an as-needed basis.

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As delivered, the oxygen depletion detector comes with latches on the door to allow servicing of internal components. It can be made more secure by bolting the door closed. For additional security, the Oxigraf ODM enclosure can be locked closed with a padlock. Beyond locking the internal components, the key panel can be disabled to restrict operation control. Entry of the proper password will allow service personnel to perform any required calibration or other maintenance operations.

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An optional internal battery and charging system will maintain operation of each oxygen deficiency monitor for one hour following a power failure. This optional feature will continue to give you the full protection of the ODM, including alarm power and any remote indicator lights.

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The O2iM unit can be fitted with a Z-Purge system and allows the unit to be used in Class 1 Div 2 hazardous area. The purge requires a nitrogen gas source for inerting purging of the housing and the O2iM housing adds a purge indicator and purge gas regulator with remote indication of purge status on a relay output.

A OxiPurge option is also available to allow purge of the enclosure in non-hazardous situations to keep outside environment from contaminating the enclosure and keep the enclosure dry with CDA or Nitrogen purge. The OxiPurge option provides a VFD display notification if purge is lost.