Sealed grow room with excessive CO2 levels

I have been growing for about 3 years now. My setup is a 7’ x 13’ sealed grow room in the corner of a 24’x28’ basement that is more like a bunker. The ceiling and walls are concrete with a 36" entry door to the space. No outside air to any of it except opening the door. I have an autopilot APC8200 controller/monitor, and a CO2 tank and regulator that are set to 1300ppm. I have three 6" inline fans with carbon filters (All replaced in the last week, 2 draw off the floor and one is closer to the ceiling, they all are setup to blow the air in a circle to go all around the room. I have a mini split to control temp, and a dehumidifier. I have 2 Spider Farmer SF4000’s and 1 SF2000 for 12 plants on a 4’ x 10’ sliding table. I grow in FFOF with Advanced Nutrients.

From the beginning 3 years ago, I have never had an issue with CO2 levels getting above 3000 unless I am in the room for a really long time, and even then, it would level out. I have not changed anything at all and have never had any type of infestation except the occasional fungus gnat, but for the last 2 cycles I have been struggling with the CO2 level never getting below 2000 and many times being up to 3500. When I built this room, I put in one 3" PVC pipe to the outside, but have never used it.

Can anyone help with what I should do, or why my plants are not using up the CO2 as they always have before? I grow 3 strains, and all of my plants look fine except my wedding cake strain has not gotten near as big while this has been going on.

Thanks, and sorry for the length of this.

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Since no one has answered yet let me update and again ask for help.

Incase people aren’t replying because they think I haven’t read the forums. I did, and I understand lockout, but my plants look good, see pic. I took the CO2 completely out of the grow room 3 hours before the lights went out last night. My PPM was 2200, I come back over this morning and my room was at 5200. I’ve dumped the CO2 for 3 days prior to this. I also put my second meter in to make sure the regulator isn’t malfunctioning, and they read identical. How is this happening? Please help

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I am not a CO2 grower so the only advice I can give you is cut off your implemented CO2 source for now…maybe something else in your room is generating the excess CO2…did some mushrooms start somewhere in the corner maybe???

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So when I built this in the corner of my second basement, I rubber sealed everything on the concrete from floor to ceiling so I don’t think there’s anything growing behind the reflectix.

Left the room with the tank sitting in the front part where my wood shop and second monitor is last night completely out of the grow room. That room was 1590 last night and 1610 this morning. Grow room was 2960 with 1 hour of light left and no CO2 tank, and it’s 4400 this morning 20 mins before the lights come on.

I’m pulling my hair out because I have to take care of them, but been dangerous human levels last 2 days.

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Please be vary careful. A member of this forum lost a friend from CO2 poisoning in a grow room.

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You should monitor the oxygen level in the basement and see if it’s below 20%. That will tell you a lot. I don’t know about basements but I was in a field where we had to go into spaces that were below ground and couldn’t go into some until air was pumped in. Maybe it’s something like that @cdsmith12 …sounds like we’re grabbing for straws here anyway.

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Thanks for the comments, does anyone know of an electronic damper that will seal when closed? My fear and reason for never setting up a CO2 dump is that bugs could crawl through the pipe. The only bug I have had in 3 years is some fungus gnats from the soil, and I don’t want anything else.