Take your time removing the sensor. Parts are plastic. They become brittle over time and can break. Slid out of the duct.

Measuring air flow in an HVAC duct can be a tricky business ... The principle behind the sensor [ItMightBeWorse] is working on is nothing new. He discovered a paper from 2015 that describes ...

From the looks of it, his hardware configuration is relatively simple. All it uses is a TSL261 Light-to-Voltage sensor connected to an Arduino with an Ethernet shield attached. The sensor is then ...