co2 levels in house reading 1200ppm

I just got a co2 monitor/controler it is a titan atlas1 before setting it up I pluged it in and set the elevation level to the proper setting and pluged in a test light to see if the co2 outlet would come on when needed. To my surprise the co2 in my house without any suplement was reading around 1200ppm. I know little about this and did try to find answers to my question before posting but didint find the answers. I did read that a occupied environment acualt will have a higher co2 level then outside. Out side my meter reads 400ppm so the metter is working correctly. I also have natural gas heat/funace, hotwater, stove. There is 2 adults and a child and a dog living in the home. Would this make my co2 level be in the 1200ppm range? should I be concerned for my familys health? If this is okay then it will be great, but if it's not then what could be causeing it and what could be the risk. Any and all accurate correct not bullshit out your ass answers would be greatly appreshiated since this is or could be a serious issue to my family pets and girls.

http://www.dhs.wisconsin.gov/eh/chemfs/fs/carbondioxide.htm

All the info you need. Hope it helps.

That article is probably spot on, no health issues at that "low" level. However you may be wasting you money with a Co2 set up if you are already running that high in the house, just intake from the house to use all of the Co2 you can. Hell for winter i am setting my room up to heat the house instead of wasting the heat, maybe you could do the same thing.....

Thank you for the links both where helpfull. I was thinking the same thing. Why run any co2 if the levels are already that high in the house. If I do boost it up to 1500, it won't take much so should get a hell of a lot more out of my tank. I most have been killing them with co2 before this using the calculatons they give to figure out how much and for how long to run co2 to get to 1500ppm considering that your level is only 400ppm. Thankyou all for your help. Much appreshaited.