Have you checked github?

https://github.com/DFRobot/DFRobot_HumanDetection

Why not?

@Reyson How are you measuring the output?  How are your forcing the maximum voltage out of the part?

PS - You shouldn't need to worry about finding the device on I2C - seems like DFRobot has taken care of that for you if you use the driver they provide.

Have you tried downloading the driver and examples from github?

https://github.com/DFRobot/DFRobot_AirQualitySensor/tree/master

The examples there seem very straightforward, so I would try one. 

The initialization code for both examples is the same:

```
I2C_1       = 0x01               # I2C_1 Use i2c1 interface (or i2c0 with configuring Raspberry Pi file) to drive sensor
I2C_ADDRESS = 0x19               # I2C Device address, which can be changed by changing A1 and A0, the default address is 0x54
airqualitysensor = DFRobot_AirQualitySensor(I2C_1 ,I2C_ADDRESS)
```

That should create an object you can query to get measurements.  

For example, you might try (in Python)

```
pm1_standard_reading = airqualitysensor.gain_particle_concentration_ugm3(PARTICLE_PM1_0_STANDARD)
print(pm1_standard_reading)
```

Which should give you the sensors reading of that value.

Hope that's helpful.

If it's still helpful, I believe you can find that library on github:

https://github.com/DFRobot/DFRobot_AS3935/tree/master