Carbon filter buying guide for a grow tent
Updated: October 2026
You have a tent, a fan still in the box, and a list of carbon cylinders on amazon.co.uk, and the first click is the one that locks you to the wrong diameter. This carbon filter buying guide for a grow tent puts the decisions in order: whether the crop is lawful, which millimetre flange you already own, how much air the tent needs, and only then whether a bare filter or a fan kit belongs in the basket. The scored rows live on the [carbon filter grow tent comparison](/hub/raised-beds-greenhouses-and-compost/carbon-filter-grow-tent). Prices are from that October 2026 scrape, in GBP. A qualifying purchase can earn a commission at no extra cost to you. We compared listings, not a lab.
You have a tent, a fan still in the box, and a list of carbon cylinders on amazon.co.uk, and the first click is the one that locks you to the wrong diameter.
You have a tent, a fan still in the box, and a list of carbon cylinders on amazon.co.uk, and the first click is the one that locks you to the wrong diameter. This carbon filter buying guide for a grow tent puts the decisions in order: whether the crop is lawful, which millimetre flange you already own, how much air the tent needs, and only then whether a bare filter or a fan kit belongs in the basket. The scored rows live on the carbon filter grow tent comparison. Prices are from that October 2026 scrape, in GBP. A qualifying purchase can earn a commission at no extra cost to you. We compared listings, not a lab.
Our top picks
| Badge | Product | Duct | Type | Listed airflow | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  AC Infinity AC Infinity 100 mm carbon filter | 100 mm | Filter only | 210 CFM | 9.0 | about £47.99 | View offer |
| Best value |  AC Infinity AC Infinity 150 mm carbon filter | 150 mm | Filter only | 410 CFM | 9.0 | about £65.99 | View offer |
 MARS HYDRO Mars Hydro 4 inch carbon filter | 100 mm | Filter only | 210 CFM | 7.3 | about £27.92 | View offer |
On this page
What you are buying
A carbon filter for this job is a metal cylinder packed with activated charcoal, usually wrapped in a cloth pre-filter, with a flange that clamps to flexible duct. An inline fan pushes or pulls tent air through the bed so odour molecules spend time on the carbon before the air leaves the room. It is a scrubber in a duct run, not a box you sit in the corner of a bedroom and hope for the best. UK hobby pages, including Greens Horticulture and Hydroponics UK, treat the filter and the fan as one system: same diameter, filter rated at or above the fan, exhaust preferably outdoors.
In this eleven-listing set, filter-only cylinders sit from about £28 to about £66. Charcoal lines such as RC412 are marketing on the bullet list, not a measured removal rate. A 100 mm filter on a 150 mm fan, joined by a reducer, is the purchase this guide is trying to stop.
UK law, housing and the plug
Cultivating cannabis in the United Kingdom is unlawful without a Home Office licence. Section 6 of the Misuse of Drugs Act 1971 is the statute, and the GOV.UK cannabis licensing factsheet says cultivation needs authorisation. A filter, a tent and a quiet fan do not create that licence. This guide assumes lawful uses: herbs, seedlings, chillies, or a small enclosure such as a 3D printer cabinet, which several budget titles in the set also name.
Renters should read the tenancy before they core a wall. Inline fans plug into 230 V through a BS 1363 plug. Do not overload an extension, and leave new circuits to a qualified electrician.
Diameter and airflow before the stars
Match one diameter across fan, filter and duct. This comparison contains 100 mm (4 inch), 150 mm (6 inch) and 200 mm (8 inch). Reducers add resistance and noise, which is why The Growers Shop duct guide argues for staying on one size. A title that prints Ø100 mm × 200 mm is a 100 mm flange and a 200 mm body length. That pattern appears on HG Power and Hon&Guan 4 inch rows, and it is easy to misread the length as an 8 inch duct.
Airflow starts from the tent, not from the star rating. UK retailers repeat a rule of thumb: volume in cubic metres, times 60 for one air change per minute, then about 25 to 35 per cent more for the filter and the duct. A worked example sits on the size guide: a 120 × 120 × 200 cm tent is about 2.9 m³, about 175 m³/h before the allowance, and about 220 m³/h after it, which those guides place on 150 mm.
Filter-only, a refillable shell, or a kit
Buy a cylinder when the fan on the floor already matches the flange. The AC Infinity 100 mm filter at about £47.99 is the top pick on combined evidence, fit and price. The AC Infinity 150 mm filter at about £65.99 is the best value, because that diameter is the one UK guides cite for a standard 120 cm tent. Budget 100 mm options, Mars Hydro at about £27.92, HG Power at about £29.99 and Hon&Guan at about £29.99, make sense only after the volume maths stays on 4 inch.
The fan kits, AC Infinity CLOUDLINE LITE at about £189 (352 CFM on the bullets) and VIVOSUN G6 at about £169.99 (388 CFM, smart control on the listing), are for buyers who do not yet own a 150 mm fan. An app does not change the licence position or the need to exhaust outdoors.
Maintenance, and when the bed is finished
The pre-filter is the part you service before the charcoal is finished. Mars Hydro, Hon&Guan and AC Infinity bullets mention a sleeve. Dust on that cloth cuts airflow before the bed is saturated. Fit it before the first run, and note the date on a piece of tape on the duct. If black dust appears on nearby surfaces, stop and check that you are exhausting outdoors rather than blowing the bed back into the room.
Common questions
Do I need a carbon filter for a grow tent?
You need one when tent air will pass near neighbours or through a lived-in room and you care about odour. The filter scrubs air in the duct. It does not cool the tent by itself, and it does not make a controlled crop lawful. If you exhaust straight outdoors from a remote outbuilding and odour is not the issue, a fan alone can be enough, though most flat and terrace growers are not in that position.
What duct size should match my fan?
Use the same millimetre size on the fan, the filter and the duct. In this set that is 100 mm, 150 mm or 200 mm. A reducer will join unlike sizes and adds resistance. Read Ø100 mm × 200 mm as a 100 mm flange and a 200 mm long body, which is how the HG Power and Hon&Guan 4 inch titles are written.
How long does a grow tent carbon filter last?
UK retailers often quote twelve to eighteen months of continuous use. That is a rule of thumb, not a promise for any ASIN here. Replace the filter when odour returns at the outlet, and wash or change the pre-filter sooner if dust has choked the sleeve. A refillable shell changes the media, not the diameter.
Is a carbon filter enough to grow cannabis at home?
No. Cultivation of cannabis without a Home Office licence is unlawful under the Misuse of Drugs Act 1971. The GOV.UK licensing factsheet covers that authorisation. Filters in this comparison are ventilation parts for lawful horticulture and for small enclosures such as printer cabinets.
What does Australian RC412 charcoal mean on a listing?
It is a grade name printed on AC Infinity and VIVOSUN bullets, sometimes with an IAV figure such as 1200+. Treat it as a buying hint. This project has no laboratory odour test, and reviews that mention thinner beds versus other brands are experience reports, not a measured removal rate.
Can I use the filter for paint fumes indoors?
Do not plan on it. These cylinders are sold for ducted exhaust. A UK review of the AC Infinity 100 mm filter reports black soot when the buyer recirculated paint fumes indoors. Exhaust outdoors, and do not use a grow-tent carbon filter as a substitute for a proper spray-booth extract system.
Related pages
Sources
Public UK sources for sizing, licensing and electrical safety, last checked on 20 October 2026. Amazon.co.uk listing lines are the price and review source for the eleven ASINs. No laboratory odour test was run.
- Greens Horticulture — grow tent fan and carbon filter size (retrieved 20.10.2026)
- Hydroponics UK — carbon filter sizing guide (retrieved 20.10.2026)
- The Growers Shop — grow room ducting size guide (retrieved 20.10.2026)
- Roots2Riches — extraction fan calculator (retrieved 20.10.2026)
- Misuse of Drugs Act 1971, section 6 (retrieved 20.10.2026)
- GOV.UK — cannabis licensing factsheet (retrieved 20.10.2026)
- Electrical Equipment (Safety) Regulations 2016, regulation 35 (retrieved 20.10.2026)
- London Fire Brigade — cables, fuses and leads (retrieved 20.10.2026)