The Big Quiet Air Purifier was an air purifier that was meant to multiply the good performance of the fan by combining it with other tricks, such as a better filter arrangement, and remote monitoring and management features (power control over MQTT, as well as actual airflow monitoring to determine filter status, verify the machine is working fully etc.), as well as an actual solid structure to hold things together (rather than just tape with the CR boxes), and even a cosmetic cover. It can also be hung from a ceiling, liberating floor space.
It had it's own domain name but I stopped paying for it, no real need. The site can be found here:
https://sites.google.com/view/bqap?usp=sharing