And largely unnecessary as most building codes now mandate exhaust and fresh air requirements where gas cookers are fitted.

That's for new buildings.

Most people don't live in new buildings.

Fair enough. Do you think it's easier to add some vent fans or retrofit a building gas->electric in every flat? It's not as easy as it's made out to be. Buildings were designed with sufficient electric service given the utilities available at the time. Buildings with gas have undersized electrics. In other words the service (transformer etc.) is likely inadequate. A massive retrofit from gas to electric cookers would be insanely expensive.

Actually, I think gas->electric is the easier one quite frequently.

Simply because adding vent fans can be a physical impossibility because there's nowhere to vent to. There's more living space on the other side of the wall (in your building or an adjacent building) so you can't vent directly outdoors, and there's no duct so you can't vent anywhere else either.

It's also not necessary. The particulate studies that measured gas stoves as being super dangerous were measured in the most impractical scenarios where the room was sealed off with plastic, and not at all reflective of basically anyone's real home.

Just buy a CO2 sensor and you'll see quickly what the issue with gas stoves is. I have one in front of my gas stove and it takes a lot longer even with ventilation / open windows that you'd think to get back to normal indoor levels.

Seriously. I always thought it was exaggeration until I bought a sensor as well. I was horrified.

A little CO2 isn't harmful at all. Are you thinking of CO?

CO2 is just an easy to measure thing but if CO2 is leaking in to the room, all the other pollutants are too. If your extraction setup was actually working properly you wouldn't notice any change in CO2 in the room.

CO2 is obviously a proxy here indeed, although it is harmful by itself.

This is not “a little CO2”. Buy or rent a sensor, go cooking without the hood set to the proper setting / a window cracked open for long enough, and you’ll be horrified.