If you could provide the Brand, model # this will be helpful to our users finding a solution.
With regards to the Avanta AAS which may be a similar product, it explains the pressure relief bung is to ensure safe operation is assured.
GBC Sci States "The flame will not ignite if any interlock is triggered. If the wrong burner is in place then a nitrous oxide acetylene flame cannot be selected. If a fault is detected, the cause is displayed by an indicator light on the front panel of the instrument" - GBC Sci
I hope this leads you in the right direction.
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