I'm a fireman's son.
A cellphone can do it - using your cellphone at the gas pump is a $10,000 fine.
Static from the carpet then you reach out to touch something and ZAP.
An electrical device cycling on - coffee maker on timer, microwave.
Old style thermostat that you rotate with the metal coil inside.
Old style phone (not phone system so much but a push button phone) - the ringer is still 120 volts.
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Running the gas without lighting the burner until the gas vuilds up and sparking it with a match if the explosion is planned or simply striking metal against metal like banging certain types of pots and pans if accidental.
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I have a real life example. My sister's kitchen was being renovated by carpenters. They left an open can of solvent in the kitchen, a very enclosed space. A spark from the water heater set off the fumes. The explosion destroyed the house ... sent flames up into the attic, spreading immediately to the entire house.
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Is the focus on the gas or on the explosion?
ie are you asking what can cause gas to explode? or are you asking what are some possible kinds of gas in a kitchen?
Gas explodes due to a spark. The rest is really up to your imagination.
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blow out the pilot light on the stove. Turn on the oven and burners. Set the coffee maker to start in an hour with some napkins on the burner instead of a coffee pot. Leave.
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Faulty regulator on the fryer, grill, flat top or oven. Gas leak from literally anywhere. Practically an entire commercial kitchen is powered by gas and heated by fire. The whole place is a powder keg