I think they were made in someone's garage after a long night of drinking from scrap metal and beer cans. The good thing is that they don't have to be particularly accurate.
Portable Handheld Manometer π for Accurate Pressure Differential Measurement
5 Review
π¬οΈ Advanced 3-in-1 Indoor Air Quality Monitor with CO2/RH/Temp Data Logging and Audible Alarm - NDIR Sensor Technology
8 Review
π§ UEi Test Instruments DAFM3B Digital Multimeter
6 Review
π Dioxide Controller for Digital Gas Monitoring
5 Review