Optional LEL Latching Alarm


This feature allows a G7 device user to choose if they would prefer their LEL sensor to continue alarming even after gas levels have returned to normal. This technique is referred to as a “latching alarm”.


Providing this option to users is a certification requirement. The feature was originally designed for an older LEL sensor technology called pellistor or catalytic bead. It was possible under rare circumstances for older pellistor sensors to be exposed to such high concentrations of explosive gas so quickly that they would cease to function. The result of this was a very high reading followed by no reading at all, even though dangerous gases were still present. New technologies such as infrared (LEL-IR) and Molecular Property Spectrometer TM (LEL-MPS) cannot experience this issue, but the requirement to provide LEL latching alarms as an option persists.

G7 gas alarms

By default, all G7 gas sensor alarms are non-latching. When the sensor reading crosses either the low or high threshold setting, G7 will trigger an alarm including lights, sound and vibration. At this point, the person wearing the device should leave the area. Note: If enabled, a high gas alert will also generate an alert in the Blackline Live portal for response by monitoring personnel. When gas levels recede back past their threshold setting, G7 will stop the device-side alarm. This is how the person wearing the G7 knows they are back in a non-hazardous atmosphere without continuously watching their gas readings. Note: If enabled, the alert sent to Blackline Live will still be active.

gas curve 1

If the default setting on a G7 has been changed to enable the LEL latching alarm, the G7 will not stop alarming when LEL sensor readings return from the high alarm threshold. The device user must manually cancel the alarm by pressing and holding on the G7’s up and down arrow buttons for three seconds. If the LEL gas alarm is not canceled by the device user, it will continue until the battery is depleted.

gas curve 2

How to enable a LEL latching alarm

Changing the LEL latching alarm setting is done from the G7 device menu, rather than the Blackline Live portal.

From the gas status screen, press the OK button twice to enter the main menu. Navigate to “Gas info,” then to “Gas options.” Select “LEL latching” from the list and confirm your selection. LEL latching alarm is now enabled for your device.

To disable, repeat the same steps. Main menu > Gas info > Gas options > LEL latching.

The setting you have chosen for LEL latching alarm will remain in place until it is changed manually. It will not be affected by power cycling the device or downloading future firmware updates.


  • LEL latching still takes place when G7 is in a mode such as pump run or SCBA.
  • LEL latching alarm will be available on G7c, G7x and G7 EXO
  • If enabled, only LEL red high alarms will latch. Yellow warning alarms will not be affected.
  • This setting is available starting on G7 firmware version 3.441 onward.