OP, please don’t assume this is your neighbors. This could be anything; it could be coming from in your house, somewhere else on your street, or a major leak somewhere in your neighborhood. The Department of Health has an ecology section that investigates weird odors and that is really who should be coming out to help you. Call 311 like yesterday and let them know what’s up.

Since you have a VOC detector, even the cheapest models give a readout and keep a datalog. When they come out, show them what you have. Good luck.