This article provides an overview of the operation, configuration, and performance of Blackline Safety’s (O2) Oxygen sensor.
The oxygen sensor is one of the most common sensors deployed in Blackline’s G6, G7, and EXO product lines. Unlike most toxic or explosive gas sensors, this sensor is uniquely configured to alert the user to a decrease or increase in the local concentration of oxygen.
The sensor is a lead-free oxygen pump sensor that is designed to detect oxygen levels by leveraging an electrochemical mechanism to measure the concentration of oxygen molecules in the surrounding air.
The sensor has a detection range of 0 to 25% v/v with a detection range of +/- 0.2%.
Any gas that displaces or consumes the oxygen in the local environment can lower the detected oxygen concentration down to zero percent, such as when CO2 is released into a confined space to extinguish a fire. When oxygen is displaced or consumed, the sensor displays the true oxygen concentration in the local environment. This is not the same as when the sensor displays an under limit (UL) state. This is caused when the oxygen in the air falls below the configured threshold and the sensor is unable to display a valid reading.
The sensor can be calibrated or bump tested with either a single oxygen gas stream or a combination of gases to allow for simultaneous testing of multiple sensors in the same cartridge. The recommended calibration gas concentration for the oxygen sensor is 18% v/v oxygen, with the balance being nitrogen.
The oxygen sensor is a reliable, consistent sensor, but it does have application limits. Users should be aware that this sensor is not intended to provide an analytical device measurement of gas concentration. Its role is to provide a consistent indication of the local oxygen level over time, a fast alert to a change in that concentration, and the direction of that change.
If the sensor is used to sample gas pipelines, storage tanks, or other confined-space vessels via the pump cartridge, Blackline recommends the use of a prefilter on the sample line before the sample enters the pump. This keeps the sensor system clear of debris, water, or any other liquids that may be in the sample volume.
When the humidity levels in the air change, it can affect how much oxygen is detected by the sensor, causing its readings to change. As humidity increases, the amount of water vapor in the air increases, making the oxygen level detected by the sensor seem lower than it actually is, potentially resulting in false alarms.
Please consult your local Health and Safety group or Industrial Hygienist for further information and guidance at your location on confined-space sampling and the recommended limits on oxygen concentration in your local environment.