What is the reason for the "planty" smell after lights out?

I have three rooms, a clone/mother/veg room and two flower's. I'm sealed up have negative pressure in each one, carbon filters, 2-3x the needed exhaust cfm and intake, that's all good. But I have always wondered why, more so in veg I've noticed, that I can smell that "planty" smell just after lights out for about 5-20 minutes. Now bear in mind I have all my exhaust running into a main room in a basement and that slowly gets sucked outside with a non-filtered exhaust. But I never have smell issues, only the lingering smell of buds after the grow room doors have been opened for some time especially in mid-late flower of course. This is just the plant smell like your fingers have after removing leaves. It is noticeable immediately after lights out and sticks around mildly for 10-20, then nothing.

Not an issue, just want to know. I can only find a few threads on this issue but no real answers. Anyone?

youre growing plants

srh88 said:

youre growing plants

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Hmmmm no, that's not it.

I want to know what process is happening right at lights out that causes the more then mild plant smell to happen through a carbon filter that always cleans 100% of the smell from the stinkiest of stains during flower.

But thanks.

Damn! I was typing out a reply on another thread and my one flower room just happened to go into night mode. The exhaust outlet from that room is right above me at my pc desk downstairs just 6-7 feet from the basements own exhaust fan that shoots it up and out. As soon as 430am hit(off time) that plant smell just hit me hard. Now just 5 minutes later it's gone.
Something happens at lights out, I wanna know.

I hope I don't start hearing voices at lights out now.

Say Jesus Save Me said:

May you be healed

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If we wanted to hear this shit we'd go to church.. go the fuck on somewhere!!!!!!

Rancho Cucamonga said:

Damn! I was typing out a reply on another thread and my one flower room just happened to go into night mode. The exhaust outlet from that room is right above me at my pc desk downstairs just 6-7 feet from the basements own exhaust fan that shoots it up and out. As soon as 430am hit(off time) that plant smell just hit me hard. Now just 5 minutes later it's gone.
Something happens at lights out, I wanna know.

I hope I don't start hearing voices at lights out now.

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Is your RH shooting up after lights out? I believe at about 65% RH and up carbon filters don't work as well, moisture blocks the pores that interact with the odors. When my RH hits 65%+ my place gets that "planty" smell, not to be confused with that "weedy" smell . Maybe that's it? Good Luck and Happy Growing!

FranJan said:

Is your RH shooting up after lights out? I believe at about 65% RH and up carbon filters don't work as well, moisture blocks the pores that interact with the odors. When my RH hits 65%+ my place gets that "planty" smell, not to be confused with that "weedy" smell . Maybe that's it? Good Luck and Happy Growing!

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Possible. But my RH in all grow rooms never goes above 60%. I will monitor the gauges at lights out for a week or so and see if there is a short dramatic rise in RH even though the memory from my gauges which records my low/hi temps and humidity have never rose above 63%. The fact that it smells immediately after lights out and only for 5-20 minutes is what puzzles me. If not RH it must be some sort of process or reaction of the plants to the lights turning off. Being my grow rooms exhaust into one end of my big room and then up and out of the house on the other end of the big room, that big room always has that charcoal/carbon smell to some degree, but the plant smell is only lights out for 5-20.

Happy luck longtime growing-something a fortune cookie might say.

This is an interesting question... I will definitely watch and see if someone knows... cause I get the same thing specially the day of water/feeding and the day after. I do not have my carbon filter hooked up yet as the dank is not there yet (day 6.5)

Hi, i notice exactly same thing, only at lights out for a few minutes, i believe its chlorophyll thats the culprit, plants release a lot of it at lights out, and that smell gets through the filter.

I think its because as soon as light disappears the plant starts its nightly processes. It takes more energy to start a process than continue so your girls do extra work which causes the smells associated with said change.

Thanks for the replies people! I think mongcheese has it right but I'm only assuming.

is it bad enough to get you caught? Or just one of those "your room stank" kinda things

No it's not bad enough to get one caught. The smell itself isn't the marijuana smell at all, I never smell that with carbon filters, it's just the smell of plants in general and it only lasts for 2-15 minutes tops and the only reason I even smell it is because I exhaust my grow rooms into my home in the winter.

Im bumping this thread from the dead because I too would like to know! I also experience a strong 'planty' smell for a period starting at lights out. I also use a CF and dont notice any weed smell. My wife says the other night 'it doesnt smell like weed...just plants...' How does this smell escape the CF and what is causing it?!

Well. They are plants

mongcheese said:

Hi, i notice exactly same thing, only at lights out for a few minutes, i believe its chlorophyll thats the culprit, plants release a lot of it at lights out, and that smell gets through the filter.

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LMAO. That is the dumbest thing I have ever heard. Plants release chlorophyl ??!! LMAO.

It takes more work to start a process then to maintain one? What? So the plants are sweating?

Maybe they are scared when the lights go off and they are darting?

Even though I have not noticed said smell it is most likely due to the plants switching to respiration only and ceasing transpiration activities. While plants respire and transpire when the lights are on, they do not transpire when the lights go off. Respiration is a chemical reaction where organic molecules (mostly sugars) are oxidized to provide energy from the broken chemical bonds. The by products of this are principally CO2 and a small number of oxidized organic molecules. This would produce a small "rush" or organic molecules, some of which are volatile and you could readily smell them. In terms if I can't smell it after 5 mixtures, I would have to attribute that to the phenomenon of human senses, discovery of new stimuli and attenuation of constant stimuli. Meaning that when the smell is "new" you can readily smell it once the body recognizes the smell it rapidly becomes accustomed to it and the intensity rapidly fades.

I thought for a second that maybe cannabis is a insect pollinated plant targeting night dwelling insects. These plants are usually dull colored (cannabis flowers are simply green) and many produce intense scents when the sun goes down. There are several plants that do this. But cannabis is an ancestor of wind pollinated plants and they continue that strategy.

That's the best explanation I can think of/ google based on what is going on at lights out.

It rly might be the process of 'sleeping', just like when you snap a brench, it releases a caracteristic smell.. and u can't feel it after a while cause u get used to it...

^ +rep for not having even the most basic spell check app.

i know this is old as fuck post but i am noticing this exact same thing and have been reading posts online for a while
closest explanation i fond was that the plant is releasing more smell because of the amount of light it has absorbed in the day and that is pushing humidity up for a small amount of time
pretty much the plant is taking one big wet fart and the carbon filter cant handle the clean up