have tank of co2 no controller help me feed my babies plz

i can afford a tank of co2 but not the controller so is there a way to calculate how much co2 im releasing? or does someone know how to feed co2 safely without controller ...how many times a day for how long? my room is 4x10 and 10ft tall 12 plants ebb and grow hydro 55 gal res 600w adjust awing avr temp 85f up to 90 in heat of day and as low as 70f at night but grow is indoors chiller keeping nutes at 70 f plz help

You could turn it on and off manually I guess. When you feel like you're going to pass out, turn it down.

You can,but it you will waste a lot more than needed and it's a pain in the ass.I speak from first hand experience,my advice to you is to just save some doe and use the tank when you get the Co2 injector kit