Indoor air-quality monitors

An indoor air-quality monitor tracks the pollutants you can’t see — fine particulates (PM2.5), CO2, VOCs, humidity, and sometimes radon — and shows trends over time so you can tie spikes to cooking, wildfire smoke, or poor ventilation. They’re popular on the Front Range where summer wildfire smoke drives PM2.5 up for days. Look for the specific sensors you care about: PM2.5 for smoke and dust, CO2 for stuffiness and ventilation, VOCs for off-gassing. Wi-Fi models log to an app and can trigger smart ventilation.