Ambient air quality indoors and outdoors

AIR project has good code and the sensors for CO2 and ozone must be out there.

Amazing air quality displays

Datalogger using SD cards vs EEPROM

You can definately store more data on a SD card cf. EEPROM chips.  MOre expensive but more functionality. A introduction to SD and the arduino

Serial Sparkfun LCD

These LCDs have issues when rebooted and display wierd characters.  Solution is to disconnect power.  Maybe adding a disconnect through a transistor may help and link to the external reset button.