CO2 Unsafe unvented?

I have a 4' x 2' x 8' (tall) closet that I am growing 16 plants hydroponically with the bubbler system with the plants extremely close together. I am trying to plan a way to suppliment CO2 to my closet, however just outside the closet is where me and my girlfriend live. We only have a 1 bedroom place and it isn't huge. I was planning on buying a 10-20 lb CO2 tank and running fans (both inside the closet and just outside) on timers to vent the space out every few hours, however there is no ventilation from outside the closet to outdoors, it just vents into our home. Is that dangerous?

Again I am wondering if the CO2 vented into my home could become dangerous in any way. My closet space is a mere 64 Cubic Feet and only 8 Sq feet and wouldn't require lots of CO2. I was also only planning on increasing CO2 levels to around 900 PPM, but again could this pose a danger?

Thank you. Please be specific as possible, safety is my first concern.

A 1000ppm is still considered safe by gov standard (osha maybe? forgot, sorry)

Even at 1500 its not that much a risk.

Do you plan on getting a controler or just guestimating?

i have a table top monitor that has an analog and RS232 output. I use the output value in a controler. But I can put the monitor in any room and see what it is.

Now I found the indoor CO2 was about twice that of the outside of the house

you will be fine but i recommend using a controller. I just received mine this morning.

this is what I got.

SENTINEL CPPM-1 CO2 CONTROLLER W/PHOTOCELL FREE SHIP - eBay (item 140257792257 end time Aug-22-08 20:30:43 PDT)

I read somewhere that dry ice put into the grow room will supply enough CO2, its cheap and safe. Can anyone validate this claim.

I'd think that the pucks might be an easier option for you than dry ice...

Also I read somewhere recently that co2 up to 5000ppm is considered safe...

What levels of CO2 are considered safe?

Carbon dioxide is not generally found at hazardous levels in indoor environments. The MNDOLI has set workplace safety standards of 10,000 ppm for an 8-hour period and 30,000 ppm for a 15 minute period. This means the average concentration over an 8-hour period should not exceed 10,000 ppm and the average concentration over a 15 minute period should not exceed 30,000 ppm. It is unusual to find such continuously high levels indoors and extremely rare in non-industrial workplaces. These standards were developed for healthy working adults and may not be appropriate for sensitive populations, such as children and the elderly. MDH is not aware of lower standards developed for the general public that would be protective of sensitive individuals.
What are the health effects of CO2 poisoning?

Occupants may experience health effects in buildings where CO2 is elevated, but the symptoms are usually due to the other contaminants in the air that also build up as a result of insufficient ventilation. At high levels, the carbon dioxide itself can cause headache, dizziness, nausea and other symptoms. This could occur when exposed to levels above 5,000 ppm for many hours. At even higher levels of CO2 can cause asphyxiation as it replaces oxygen in the blood--exposure to concentrations around 40,000 ppm is immediately dangerous to life and health. CO2 poisoning, however, is very rare.

Carbon Dioxide (CO2): Environmental Health in Minnesota