Personal O2 Monitor Model 55

Sierra Monitor’s Model 55 is a portable, self-contained, lightweight, battery-operated personal Oxygen (O2) deficiency monitor. Model 55 is an easy-to-use monitor that does not require any adjustments by the user other than routine calibration.

The monitor reads true oxygen percentage in the presence of any diluent, including humidity. The Personal O2 Monitor Model 55 will not be considerably affected by barometric pressure changes caused by elevation or weather changes. When Oxygen percent falls below 19.5%, the large LCD digital display will be augmented by an audible alarm. The red LED will also turn on to provide visual indication of oxygen deficiency. Besides the Oxygen deficiency alarm, the Model 55 also includes an alarm to indicate low battery voltage or low sensor output.

Personal O2 Monitor Model 55

  • Single Off-the-Shelf 9 V Battery – Reliably operate and change batteries with ease
  • Compact, Lightweight Design – Provide proper and accurate operation while attaching easily to a user’s belt
  • Self-Diagnostics – Lower maintenance costs
  • Easy Sensor Cell Replacements – Lower cost of operation by having readily available power for long term use
  • Temperature-stable and Insensitivity to Barometric Pressure – Confidently work in confined areas knowing that a user will not be hindered

Specifications for Personal O2 Monitor Model 55


  • OXYMAXTM oxygen concentration transducer


  • 3 digit LCD, O2 %, in air front 0% with low battery indicator


  • 3% of full scale from 5o to 122oF (-15o to 50oC)
  • 4% of full scale from 32o to 122oF (0o to 50oC)


  • 10 seconds to 90% indication

Sensor Life

  • 21 months in ambient air

Pressure Sensitivity

  • 0.33% O2 change for 3000 ft. elevation or change or 75 mm Hg barometric change

Operating Temperature

  • 32o to 122oF (0o to 50oC)

Calibration Adjustments

  • Calibrate both internal and external sensors against dry O2. Both calibration adjustments are with a jeweler’s screwdriver


  • Audible: 72 dB rating (Factory set to alarm below 19.5% O2)
  • Visual: LED Light


  • Alarm earphone jack, external sensor jack


  • 9 V alkaline, typically 200 hours of life

Optional Remote Sensor

  • Sensor, housing and circuitry provided with 20 ft. cable


  • Two-piece, molded high impact plastic

Interfering Gases

  • Ozone, chlorine and highly oxidizing gases will interfere to the extent of their oxygen equivalent. Highly corrosive atmosphere will cause premature failure


  • 5.7 x 3.5 x 1.4 in. (14.5 x 8.9 x 3.6 cm)


  • 11 oz. (312 g)

How to Purchase the Personal O2 Monitor

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