plant death at 5000 ppm
yes you can use short blasts from your tank until its gone several times a day use a fan to pick up the co2 and move it around or yoy could use the yeast,sugar,water method 2 liter bottle with air tight tube placed in cap & siliconed run the tube to a cup of water and put it in the water 3 in under put 2 cups sugar and 1/2 tsp BREWERS yeast fill with warm water and cap to hose wait 30 mins and shake bottle watch for bubbles in cup recipe can be multiplied for a larger area useing a 5 gallon bucket or a 35 gal trashcan depends on how much co2 you need

or

run a coleman lamp in your room this is cheep and easy but makes alot of heat
theres a million ways to get co2 for under $150 check the faqs

good luck