QFM-333 Oxygen Deficiency / Enrichment Monitor and Alarm

The QFM333 continually monitors the air surrounding the sensor filter on its base and provides visual and audible alarms when the monitored concentration of oxygen falls below the pre-set 'Low Oxygen' or rises above the pre-set 'High Oxygen' alarm levels.


The QFM330 Oxygen Monitor may be used as a stand-alone device with its own audible and visual alarms, or linked to other repeater modules to mimic the condition of the monitor. Repeater modules can be connected to the QFM330 and located outside the monitored area to warn users at the point of entry. The system can be fully customised to allow multiple location monitoring and further modules can be easily added at a later date to expand the scope of the system.

Key Features
  • Oxygen monitor unit operates continuously for two years and cannot be switched off, giving maximum user protection.
  • Built-in visual and audible alarms with separate ‘low’ and ‘critical’ alarm states.
  • Internal Audible alarm is 85dBA at 30cm.
  • Long life oxygen sensors provide 24 months operation in normal use.
  • Audible/visual alarms at the monitoring point not only at a remote location.
  • Oxygen enrichment, deficiency and high/low monitoring options.
  • Simple & secure connections to repeater modules using a pre-wired plug in connector (up to a maximum of 100m).
  • Modular system which allows the user to completely design and customise the system to suit his exact requirements.
  • Suitable for use in high magnetic fields.

Operating conditions Temperature -5 to + 45 oC (-20 to +50 at lower accuracy).

Humidity 0 to 99% RH non-condensing

Pressure range atmospheric +/-10%

Case material Black anodised aluminium with GRP front panel.

Dimensions (excl. bracket) 165 (H) x 90 (W) x 55 (D) mm.

Weight Approx. 550 gms (0.55 Kg).

Indications 5 LEDs and Audible Alarm

Electrical Connection Socket on top face for connection only to approved dedicated units.
Standard Alarm Thresholds Low Oxygen 18% oxygen
High Oxygen 22% oxygen. Special levels available upon request.
Response time typically less than 10 secs. for alarms to activate on a calibrated QFM333, when sensor subject to 18.2% or 22% oxygen test gas

The sensor pack (QM330RS) has an expected operating life of two years in air whilst the battery lifetime depends on the proportion of its life the QFM333 spends in an alarm state. For a battery life of two years of normal operation the QFM333 typically can spend 26 days in continuous `Low Oxygen’ or `High Oxygen’ alarm state