When hfc-134a become combustible in a mobile air conditioning system.?

In an oxygen enriched environment.

Explanation:

The amalgamation of HFC-134a with a high concentration of air at elevated pressure can turn combustible in the existence of an ignition source, that is, an oxygen-enriched environment. Thus, at high-pressure condition in the presence of oxygen in a mobile air conditioning system results in combustible HFC-134a.

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layer 3 is younger than layer 6.