Over the past year or so, Hubitat added a capability to support Gas Detector. Yay. And HSM supports Gas sensors, in addition to smoke and carbon monoxide. Double yay.
However I've noticed:
there is no corresponding tile in Dashboard for gas (a fact @kahn-hubitat has pointed out elsewhere)
there is no virtual gas sensor
There are workarounds for both, but it sure would be good if Hubitat could address these.