I thought it would be fun to document some of my mistakes and solutions to them, so lets jump right in with where things stand.

I started with the Arduino Uno just to get up to speed with the platform. After a day or two with that on a breadboard I ordered some Arduino Pros to use in the final product. I arbitrarily picked the 5v versions since thats what I assumed wouldn't matter. The MQ-2 analog sensor is a 5v device, so I figured a 5v micro would work just fine. Everything was fine running off of USB but as soon as I switched to a 3.7v LiPo battery (via the RAW input on the Arduino Pro) I noticed my ADC measurements from the MQ2 were not anywhere as sensitive as when I was running off USB/5v. Well, I assumed the Arduino Pro had a boost circuit that would boost the 3.7v to 5v for the Vcc pin... oops! So my challenge now is to either use a boost circuit (Like one from Adafruit) or to switch to the 3v Arduino Pro and switch to a different sensor. The MQ2 seems pretty flaky anyways so I ordered 2 new smoke detectors from Mouser that are a lot more expensive but run at 3v. One has analog output and the other is i2c based. Ill see which one seems to perform better and update the project then...