$50 · Amazon Air Quality Monitor

We bought this to monitor the particulate matter in our house from our wood stove. Turns out, the wood stove adds almost nothing but we did see the air decline from forest fire smoke and could also see that we had occasional spikes in the volatile organics reading caused by cooking! Anyway, it still seems to be working fine and since we no longer worry about our wood stove, we no longer need it. The system links to your Amazon Alexa and you can set up alarms. Also provides a daily graph showing all the measured parameters from the Alexa app.