I used the study linked above when looking for an indoor air quality monitor about a month ago focusing on the Field R squared numbers. I didn't consider the sensors that cost thousands of dollars as they were out of my price range. Based on this chart http://www.aqmd.gov/aq-spec/evaluations/summary-pm I narrowed it down to the Atmotube Pro, Kaiterra Laser 2+ Egg and PurpleAir PA-I-Indoor. I chose the Atmotube Pro - since it is built as a portable device (comes with a carabiner) and had good R Squared numbers for PM1.0 and PM2.5. The app is excellent and gives me a notification about once a week to run a reading so that I have an ongoing chart of the air quality measures. I don't know what the market size is for any of these air quality devices but I would think at some point they are going to become more commonplace in homes.