how big is your room, a 512 cu. ft. room should have a 20lb. co2 tank last 1 - 2 weeks. i would get a secondary co2 testing kit such as this one (i will post) and make shur e your staying in the 1500 to 1800 range. it should only take six min. to get that ppm rating in a room the size i stated above.
All this info was what the local hydroponic store told me so i could be wrong. i am setting up co2 in a couple days~
Yes im a ganja planter, call me di ganja farmer, deep down inna di earth where me put di ganja, babylon come and light it up on fire ~ Marlon Asher