We have an indoor purple air sensor with a color gradient indicator (from green all the way to purple and many gradients in between). Exactly as you've said we are surprised at the number of times cooking has turned the air quality horrible indoors. Further we are able to see how when air outside is smoky from wildfires that the internal air filters are doing their job. Definitely worth the cost for us in the Bay Area: https://www2.purpleair.com/products/purpleair-pa-i-indoor