A "public good" is, technically speaking, one which is "non-excludable and non-rivalrous". In a dense urban area, firefighting is clearly a public good, becaus

A "public good" is, technically speaking, one which is "non-excludable and non-rivalrous". In a dense urban area, firefighting is clearly a public good, because to stop the building owned by Paying Client A burning down, you need to stop the building next door owned by Non-Paying Client B burning. You can't just stand around and make sure it doesn't spread across the property line to paying clients. Or to flip it around, paying firefighters to fight your fire benefits everyone around you. In non-urban areas, at least if there's no serious risk of wildfires, firefighting is clearly not a public good. If your farmhouse start to burn, it's not going to threaten anyone but you, and paying firefighters to save it doesn't benefit anyone but you. And in a (rare?) case of economic theory working in practice too, that's what we often observe: Rural fire departments often require fees to be paid, and won't fight fires if you haven't paid up. (That being said: Just because rural firefighting isn't a public good doesn't mean it shouldn't be communally funded out of general taxation. Lots of what governments spend their money on aren't actual public goods.)