air quality

Sometimes a sensor lies about what model it is: the SEN55 that said SEN54

Some AIR-1 units report themselves as a SEN54 over I2C even though the module inside is a SEN55, so ESPHome shut their NOx sensor off. It turned out NOx had never worked on those units at all. A small override option settled whether the hardware or the register was lying, and it ships in ESPHome 2026.7.2.

Building an air quality LED indicator for the AIR-1

The AIR-1 has three onboard RGB LEDs, so I made them show air quality at a glance. The feature itself is small. Getting there took longer than it should have, because I kept fixing things that weren't the problem. These are the dead ends and where it ended up.

Two days of ceiling dust, measured in eight rooms

I spent two days cutting sheetrock, disturbing old insulation, and scraping popcorn ceiling in the upstairs bathroom, with eight Apollo AIR-1 sensors watching the whole house. The two rooms off the bathroom spiked 20 to 30 times over, and the return air lifted every other room too. The room-by-room data, and why I wore a P100 the whole time.