Inline Fan and Carbon Filter Kit: How to Size and Build Your Ventilation Setup

Once you've decided a proper inline fan and carbon filter is the right call rather than a hardware-store exhaust fan -- and our inline fan vs Bunnings guide covers why that decision matters -- the next question is simpler but still trips people up: what size, and what actually goes together. This is the practical buying guide. No spec-sheet jargon, just what to buy for the tent you actually have.

Match the Diameter First, Everything Else Second

The single most common mistake in a first ventilation setup is buying a fan, filter, and ducting in three different sizes and trying to make it work with reducers and adapters. Every size change in a duct run creates turbulence and restriction, which is exactly the airflow loss you're trying to avoid by buying a proper fan in the first place.

The fix is simple: pick one diameter and buy your fan, your filter, and your ducting all in that size. If your tent has a 150mm port, buy a 150mm fan and a 150mm filter. Adapters exist for when you genuinely need them, not as a default.

Sizing by Tent

This maps to the most common home grow tent sizes used in Australia. As a general rule, you want to fully exchange the air in your tent every 1 to 3 minutes -- but for a first setup, matching the fan size to your tent size below gets you in the right range without needing to calculate tent volume by hand.

60x60cm to 80x80cm tents (propagation, small tents)

A 100mm fan and filter is the standard pairing here. At this scale, airflow demand is genuinely low -- you're moving a small volume of air and managing modest heat load from a smaller light. The Air Mixed Flow Fan is available at 100mm and is the practical entry point, paired with the CarboAir 50 at the same diameter.

100x100cm to 120x120cm tents (the most common home setup)

150mm is the standard size for this tent footprint, which covers the bulk of home hydroponic setups in Australia. A 150mm Systemair RVK or Revolution AC paired with a 150mm CarboAir 50 or Rhino Pro is the right scale here. If noise is a genuine concern -- apartment living, shared walls -- the JB Quiet range starts at 200mm and is worth the step up in size purely for the acoustic benefit.

150x150cm tents and larger

200mm becomes the practical minimum here, and 250mm if you're running two lights or pushing higher wattage per square metre. The Blauberg ISO MIX covers 150mm through to 315mm in one range, which is useful if you're not certain whether you'll expand the setup later -- buying into a range that scales avoids a second purchase down the track.

240x120cm and multi-light rooms

At this scale you're managing genuinely high heat load from multiple fixtures, and the Blauberg Primo 400, the largest fan in the standard range, or the Revolution EC for its variable speed control under sustained heavy load, are the right tier to be looking at.

Carbon Filter: Match It to the Fan, Not the Tent

It's tempting to size a filter to the tent the same way you size a fan, but the filter actually needs to be matched to the fan's output, not the tent's footprint. A filter that's too small for the fan attached to it creates exactly the restriction problem this whole kit is meant to avoid -- airflow gets choked at the filter before it ever leaves the duct.

Buying the fan and filter in the same diameter, as covered above, gets this right by default in most home setups. If you're running a larger fan than your tent size alone would suggest -- because you want headroom for a future light upgrade, for example -- size the filter up to match the fan, not down to match the tent.

What a Complete Kit Actually Includes

• The fan -- mounted at the top of the tent, pulling air out through the filter and ducting.
• The carbon filter -- connects directly to the fan inlet, the first thing air passes through before the fan pulls it along.
• Ducting -- flexible ducting in the matching diameter, running from the fan outlet to wherever the air is being vented (a window, a roof space, or simply circulated back into a larger room).
• Duct clamps -- to seal every join. An unsealed joint leaks both air and smell, undoing a chunk of what the filter is there to do.
• A speed controller (optional, but genuinely worth it) -- the JB Fan Speed Controller for a straightforward manual setup, or the GAS EC5 for automated, temperature-driven control that ramps the fan up only when the tent actually needs it.

Intake: The Half of the System People Forget

An exhaust fan pulling air out only works if air can get back in. Most tents have passive intake vents built into the lower sections specifically for this -- check that yours are open and not blocked by anything stacked against the tent. For larger setups or rooms without a tent's built-in vents, a second smaller fan running as an intake, or simply a gap left under a door, completes the airflow loop. Without adequate intake, your exhaust fan works harder for less airflow, and the tent can run negative enough pressure to make the walls visibly suck inward.

What to Buy at Each Tent Size

For a standard 1.2m x 1.2m tent, the Air Mixed Flow Fan paired with the CarboAir 50 in matching diameter is the budget-correct combination, buying mismatched diameters between fan and filter is the most common sizing mistake at this stage.

For larger rooms or where noise matters, step up to the Blauberg ISO Mix or JB Quiet, and for genuinely large multi-tent setups, the Blauberg Primo 400 is the top of the range here. Add a fan speed controller regardless of size, so you're not running full extraction around the clock when the room doesn't need it.

Frequently Asked Questions

What size inline fan and carbon filter kit do I need for a 120x120cm tent?
150mm is the standard size for this tent footprint and covers the large majority of home hydroponic setups in Australia. Buy the fan, filter, and ducting all in 150mm to avoid restriction at mismatched joints.

Can I use a smaller carbon filter than my fan?
No -- this is the most common kit-building mistake. The filter needs to match or exceed the fan's rated capacity. An undersized filter restricts airflow at exactly the point you're trying to keep clear, which reduces the effectiveness of the whole system, not just the filtration.

Do I need a separate intake fan?
For most single-tent home setups, no -- the tent's built-in passive intake vents are sufficient when your exhaust fan is properly sized. Larger rooms, sealed spaces without dedicated tent vents, or setups running close to the top of a fan's capacity benefit from a small dedicated intake fan to balance the airflow.

Should the fan go before or after the carbon filter?
The filter sits first in the airflow path, directly on the fan's inlet side, so air passes through the carbon before the fan pulls it through and pushes it out via the ducting. This is the standard, correct configuration for odour control.

How do I reduce noise from my ventilation kit?
A speed controller is the most effective single addition -- running a fan at 60-70% speed most of the time, only ramping to full speed during the hottest part of the day, meaningfully cuts noise. An acoustic duct silencer fitted between the fan and the rest of the ducting helps further. Choosing a fan built specifically for low noise, like the JB Quiet range, also reduces the baseline you're starting from.

Not sure which fan and filter combination suits your specific tent? Email us at hello@apexgrow.com.au with your tent size and we'll point you to the right setup.