MQ135 & ADS1115 Working on Raspberry Pi. Measurement in PPM.
MQ135 (Gas Sensor) ADS1115 (Analog-to-Digital Converter)
Datasheets: https://www.olimex.com/Products/Components/Sensors/SNS-MQ135/resources/SNS-MQ135.pdf http://www.ti.com/lit/ds/symlink/ads1115.pdf
Application: They are used in air quality control equipments for buildings/offices, are suitable for detecting of NH3, NOx, alcohol, Benzene, smoke, CO2, etc. Measurement in PPM.
Original creator of this library: https://github.com/GeorgK/MQ135
Apache License 2.0, all text above must be included in any redistribution