Using Multiple SEN0463 Geiger Counters

I am using DFRobot's Gravity Geiger counter for a project. I'd like to use two of them at the same time. One will be used as a control to see what regular radiation levels are, and the other will be covered with a material to block radiation. I'd like to compare readings from both to see how well the material is working at blocking radiation.

I feel like it is probably a simple solution to read from both sensors at the same time, but I'm not sure what I need to change in the sketch to make this work. Also, I imagine that I'd have to plug each sensor into a separate pin on the Arduino. The default pin to use is D3. Based on the code provided on the Geiger Counter project wiki, what should I edit to make two Geiger sensors work at the same time.