C'mon now L.G.I., I respect you and most of the advise you
give people; but don't scare the girl. Plants respire very little
Co2 & nowhere near enough to be dangerous to pets or
humans, especially w/ only 3 plants in a well ventilated
room. You can safely work in a
sealed grow room
cranking 1500ppm of Co2 with no problem; at the very
worst, maybe a little light headedness.
From the web: (*highlights are mine)
do they release enough co2 to be dangerous to pets or humans?
Dangerous COā levels start at 5,000 ppm, and serious effects occur at 40,000+ ppm.
*Even in a completely sealed room with hundreds of plants, COā levels from respiration alone would not reach dangerous levels.
Humans exhale much more COā than plants at nightāaround 20,000 mL per hour compared to a plantās 50-200 mL.
Cannabis plants do not release enough COā during the dark period to be dangerous to humans or pets.
How Much COā Do Cannabis Plants Release at Night?
A mature cannabis plant may release 50-200 mL of COā per hour through respiration.
A dense canopy (1 m²) might increase COā levels by 50-200 ppm overnight *
in a sealed grow room.
In a ventilated space, this COā is quickly diluted and does not pose any risk.
Is This Dangerous?
Dangerous COā levels start at 5,000 ppm, and serious effects occur at 40,000+ ppm.
Even in a completely sealed room with hundreds of plants, COā levels from respiration alone would not reach dangerous levels.
Humans exhale much more COā than plants at nightāaround 20,000 mL per hour compared to a plantās 50-200 mL.
The Oā uptake is relatively low, much less than what a human or pet breathes.
A dense canopy of cannabis plants in a sealed room could slightly reduce oxygen levels, but not enough to cause concern in a ventilated space.
Key Takeaways:

Cannabis plants DO take in oxygen at night.

They release COā as a byproduct of respiration.

In a well-ventilated grow room, this is not a problem.

If a grow is completely sealed, oxygen levels could drop slightly, but not dangerously.