atmospheric nh4 level

[Jonatha-Varjao]

Hi zesteros, amazing job/code with this project.
Im working with somethin near to what you have done, but i'm trying to measure nh4 gas volume during a procedure called "arrastamento", i'm gettin the nh4 ppm levels, but i have a question on your header file on mq135 library. You defined "#define atmNH4 15" is this acurate or only for calibration purpose ?

Thanks.

PS: i have to find out the concetration of nh4 in my experimental room, calibrate the sensor and then start measuring ?