woodsmaneh said:

You bet it is, max allowable for human exposure is 5000 PPM, I work in mine all the time.

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GeneticFreak said:

Makes me feel like shit at as little as 1200. IMO it's not safe so I vent my room prior to working in there. My ears start popping and I get mad pressure in my head. I've also felt anxiety after being exposed to higher levels of co2. My plants never seem to want to need more than 900 to 1000ppmz. I think everyone is different but for me I know my limits. If you going to enrich with co2 you need to move your air pumps out of the room.

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