Air Quality direct to PI

Trying to read the Air Quality sensor using the python code - SDA/SCL and 3V/Ground connected from Pi 3 through I2C hub to ADC, LED on ADC is lit, then ADC connected via Grove cable to sensor.

When I run testAirQualitySensor.py, I get:

Traceback (most recent call last):
File "testAirQualitySensor.py", line 22, in <module>
ads1115 = ADS1x15(ic=ADS1115)
File "/root/SDL_Pi_AirQualitySensor/MADS1x15.py", line 137, in __init__
self.i2c = Adafruit_I2C(address)
File "/root/SDL_Pi_AirQualitySensor/Adafruit_I2C.py", line 43, in __init__
self.bus = smbus.SMBus(busnum if busnum >= 0 else Adafruit_I2C.getPiI2CBusNumber())
IOError: [Errno 2] No such file or directory

What am I missing?

Thanks!
Clay Jackson
clayj@nwlink.com