CO2 without a PPM meter

I've read many posts including the instructions that came with the CO2 regulator. They all talked about how long to leave to the CO2 on....

None of them said how long it will take the plants to use this amount of CO2.

I'm curious because I want to delay turning my fan back on by 10min, 15 min, 30min....

its not like they will necessarily use all the co2 before it refills, it will just keep the ratio of oxygen to co2 high for greater respiration for the plant..

think of it like this, if you are taking a jog in the mountains, because of the elevation there is less oxygen in the air, so you will be less productive and breathe harder.. its not that you can use all the oxygen in the air, but the air is "thinner" so you have to work harder to utilize that oxygen..

if you are jogging at the beach it will be much easier and you will be able to go farther faster because there is a higher ratio of oxygen in the air, thus you are more productive..

you will never use all the oxygen in the air, whether on the beach or in the mountains, but if there is more oxygen in the air on the beach, every breath you take will allow you to extract more energy, and you will do less work..

hope this makes sense

In Ed Rosenthal's book Marijuana Success Indoors he writes, "In Holland, where grow rooms are continuously cooled using powerful fans evacuating heated air, CO2 is rarely used."

How many people use the stuff? & Why?

Does it increase THC? or just Bud size?

Also does anyone have any advice on cycle times? Time on & Time off. i.e. 5 min on 5 min off every hour....

it increases yield and shortens flower time.. when you live in holland and have a massive warehouse of 30000 plus plants, you are not too concerned with a little extra buddage