Owner must be smoking too much of their own product. Isn't it an unwritten drug dealer rule, to not consume their own product? Plants also need fresh air (in this case they need CO2).

There also will be humans working in there. You need to research YOUR applicable code.

Life was easier when plants were grown outside......

Will people ever walk through there? If so, you need ventilation (fresh air).

Dude....why would you want to ventilate the weed barn??? That defeats the purpose.

--sorry, couldn't resist.

Many of the new stringshoe, independent cannabis growing "barns" directly inject CO2 to promote faster growing conditions, in some cases at high enough ppm to cause potential adverse health effects, whether by displaced oxygen or co2 toxicity if someone were in the "barn". Is it a good idea for safety? No. But then again, these folks don't seem to be too worried about OSHA and codes. It's only a matter of time.

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Not making a decision is a decision in itself

it is general knowledge that smoking marijuana messes up brain cells but what I don't know is what type airborne contaminants are generated by marijuana plants during their growth aside from the introduction of carbon dioxide introduce by the growers to stimulate plant growth. If the owner is worried about excessive CO2 levels, then you need to determine the generation rate of the CO2 by the grower and base your ventilation rate to a safe level of the CO2 within the barn. In my youth I worked on farms and ranches and all these barn are far from being air tight.

I attended some local ASHRAE meetings with a presenter who designs such facilities. Yes, the owners/operators typically have exactly the knowledge and braincells as the ones the OP seems to deal with. Their business plan typically is: Step 1: grow weed. Step 3: profit. They just have to figure out step 2..... they all seem to be weed-smoking high-school dropouts that somehow remembered there is profit in selling weed and now want to realize their dream.

They all seem to be surprised that where weed is legal, the margins are much lower than where it is illegal. Duh!

But from an engineering (and biology) point of view they try to optimize for THC content. This is far from what grow outside in nature. They basically tightly control light (artificial), CO2, humidity, temperature throughout the different grow stages. It is a lot more than just ventilation. Really, someone who really knows weed production should design this or at least provide the required parameters.

Assuming this is in a State with legal weed production, you should review the code and work with JHA to find the ventilation requirements. Humans will work in there, so yeah, can't overdo the CO2.

I'll echo what EnergyProfessional has stated - I've worked with a number of different facilities and the level of detail is very low outside of anything besides the weed itself. Luckily most of the project I'm working on for cannabis are run by third parties who are in the business of setting up grow operations correctly and safely and it's never really been a concern for us.

Suffice it to say - I don't doubt they would unknowingly, or even knowingly in some extreme cases (how extreme I don't know), create unsafe working conditions in the name of lowering operating costs, avoiding further investment expenses, etc.

Weed guys and crypto bros are about even for the high-in-the-sky plans with zero detail, understanding, or budget to get it done.