Co2 Questions

I'm growing seven plants, from seed, in a 8x4x2.5 box, designed specifically for growing. I'm using a 465 cfm squirrel cage fan and have an intake fan like the one in the image, mounted into the wall (the stand was removed)
http://www.capitolsupply.com/ImageServer.ashx?t=product&h=200&w=200&imageid=CS8165478. The intake is connected directly to an AC window unit, which I toggle between cool and fan setting, depending on the temp.

I plan on purchasing a Co2 test kit, but does my ventilation seem sufficient, or will I encounter problems due to my Co2 levels later in my harvest?

...your not going to be able to monitor your co2 levels without a monitor. To properly enrich your room with co2, it will call for a 1500 ppm during all daylight hours. No co2 is needed while they sleep, only while they photosynthesize.

...I've found it impossible to maintain a 1500ppm with a constant exaust going. You'll need an airtight room for best results.