How to Size an AC Infinity Carbon Filter
Carbon filters scrub exhaust air for odor control before it leaves the grow space. The filter sits inline with the
Cloudline fan on the exhaust path, drawing tent air through a bed of activated charcoal that adsorbs terpene and odor compounds. The two decisions are filter diameter (must match the fan duct) and tier (Premium for one-cycle simplicity, Refillable for long-term cost savings, XL for high-load situations).
Filter Sizing Reference
Premium vs Refillable
Premium filters ship as sealed units with Australian RC-48 virgin charcoal pre-loaded. Replacement is a one-step swap at end of life (typically 12-18 months under moderate use). Refillable filters cost more upfront but accept bulk carbon refills, which drops the ongoing cost per harvest by roughly 50 percent over a multi-year build. XL variants double the carbon bed depth and add 25-30 percent more service life, which is the right pick for high-CFM applications or rooms with heavy odor loads.
For a full walkthrough of how the filter, fan, and ducting interact and how to lay out an exhaust path that doesn't choke the fan, see the
AC Infinity air filtration kits guide. The
humidity control article covers how exhaust scrubbing affects room moisture and what to balance against.
Related Guides
For cross-brand carbon filter options including Phresh, Can-Filters, and Phat Filter, the broader
carbon filters page lines up the alternatives.
Frequently Asked Questions
What size carbon filter for a 4x4?
Use a 6-inch carbon filter to match the standard 6-inch Cloudline T6 fan on a 4x4 tent. The 6" Premium is the default pick. Step up to the 6" XL if the room runs heavy odor loads (large mature plants in late flower) or if the fan is running at high duty cycles where extra carbon bed depth extends service life.
Premium vs XL, when do I need the extended bed?
The XL doubles the carbon bed depth. Use it when the fan is running at 60+ percent duty cycle most of the day, when the room has high odor load (more plants than the tent footprint comfortably supports), or when you're stretching service life on a hard-to-access roof exhaust run. For typical 4x4 tents with 4 plants and moderate fan speeds, the standard Premium is enough.
Refillable vs Premium, what's the cost difference?
Refillable filters cost more upfront, but bulk carbon refills run about half the price of a sealed Premium replacement over a 2-3 year build window. Break-even is usually the second refill, around 24-30 months of use. For a single-cycle home grow, the Premium is the simpler call; for ongoing multi-year setups, Refillable pays back.
How often do I replace the carbon?
Plan for 12-18 months under moderate use (4-plant 4x4 tent, fan at 40-50 percent duty cycle). The XL stretches that to 18-24 months. Signs the carbon is exhausted: odor starts breaking through the filter, or the fan struggles to maintain negative pressure even at higher speed. Pre-filter cloth should be replaced every 3-4 months separately.
Does the pre-filter cloth need washing?
It can be vacuumed clean once or twice for surface dust, but most growers replace the cloth outright every 3-4 months. The cloth catches large particles before they reach the carbon, so a clogged pre-filter is what kills fan CFM, not exhausted carbon. Keep a spare pre-filter cloth on hand.
Can I run the filter on the intake side?
Yes, but it's much less common. Carbon filters on intake scrub incoming room air (useful in basements or rooms with their own odor sources) but don't address the tent's own odor signature. The standard setup is filter on exhaust, since that's the path that controls what leaves the tent. Some commercial builds run filters on both sides for sealed-room operations.
Will an AC Infinity filter fit a non-AC Infinity duct?
Yes. Carbon filters are sized by duct diameter (4", 6", 8", 10", 12") and connect with a flange that fits any standard duct of matching size, regardless of brand. The AC Infinity 6" Premium connects directly to a Hyper Fan or VIVOSUN 6" inline fan without adapters.
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