Those claims have been debunked as being misinterpreted. If you ran a gas stove for 24 hours then yes the amount of NO2 would be illegal outside. But this doesn't consider time-adjusted emissions but rather peak emissions. So you'd have to combine all of that into a single continuous blast, which isn't the case.

As for asthma, current U.S. federal agency involvement on the subject does not identify a connection between cooking with natural gas stoves and the risk of asthma development or direct association with asthma attacks.