Let’s just say I wouldn’t want to have been within two blocks. The drama is anything including a cell phone or static electric discharge in the area could mean BOOM. You also have floor drains etc to consider which in some areas run outside or underneath buildings into the city storm drain system. As I said gas naturally lays low. Something as simple as weather conditions can mean more so.
No, natural gas does not lay low, it is lighter than air and tries to escape, it wants out, it does not puddle and settle into floor drains and basements and under buildings, even under a house that has had a long term gas leak (natural gas), it always escapes through the vents and openings, it takes an effort to trap it.