Ventis MX4 Personal Multi-Gas (LEL-CO-H2S-O2) Air Monitor Charger (Read)

Description

Charges up fine. Functions.
I did go through testing it and from what I understand,
The O2 sensor is failing. My guess anyway.
As you can see in one of the pics,
every time it starts to calibrate, the O2 reading shows F
and the alarm goes off.
Easy fix if you want to repair it.
Sensors can be replaced.