Exhaust fan CFM and unit’s capacity

Hey, fellow growers. Does anyone know the CFM rating for the exhaust fan in the Grobo and the capacity of the unit itself also in CFM?

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I checked airflow with an anemometer and found almost 400fpm exhaust with 300fpm coming in. Hard to get a steady reading but seemed close




If the CFM from the fan appears to be adequate for the unit given its capacity, then the only logical reason left as to why the there is a smell it’s because the filter system is not sufficient.


The filters do have a finite amount of carbon that only lasts so long, that’s also a factor. I’ve noticed after 2-3 grows it doesn’t work as well (if at all).

The unit is also not 100% sealed, so some air will escape through cracks and seams and some smell along with it.

What I have been doing to prolong the life of the carbon filters is to only put it in place after she’s started to flower, so it’s not running (collecting dust) the rest of the time when it’s not even necessary.


The carbon filters were manufactured to last through one grow, its supposed to be changed every 3-4 months for best results.
Some people just use there’s twice after finding out it outlast the initial intention of its life cycle!

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Grow was in its third week from being planted and the plant was under two inches high when the smell started to become noticeable. Carbon filter was brand new off the package. I remember posting to Community at the time pictures and comments about the smell. There’s no way going around this issue- the odor suppression system is inefficient.

Have you tried it with another strain? Some strains are very pungent. I have never smelled anything from my unit with kush n cookies but, have you tried ona?


Two jars of Ona, activated charcoal outside the vents, and beach towel draped over front of unit. Going to install a fan with filter soon. This is my first grow. It’s a GSC, and I’m gonna try Northern Lights next time.

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Let us know if there is a difference in the smell when you switch strains.