G-Tools 125mm 2-Speed Inline Extractor Fan220/400 m³/h

The G-Tools 125mm 2-Speed Inline Fan gives you genuine control over your grow-room climate without buying a separate fan controller. Two independent motor windings deliver either 220 m³/h or 400 m³/h on demand - ideal for growers who need to dial back extraction noise or heat loss during colder months.

Most extractor fans run at one speed and leave you to manage airflow with a separate speed controller or by choking the ducting. This fan takes a different approach. Two separate windings inside the motor mean the low setting is a proper electrical low speed, not a throttled version of the high setting. That preserves motor efficiency and reduces the hum you would otherwise get from a controller winding down a single-winding fan.

At 400 m³/h on high speed, the 125mm collar size suits grow tents or small rooms up to roughly 1.5 m × 1.5 m × 2 m, turning the air over every 20-25 minutes when paired with a carbon filter. Drop to 220 m³/h in winter and you halve heat loss while still maintaining negative pressure. That second speed is also useful if the fan is sited close to a bedroom - noise at the lower setting is noticeably reduced.

Installation is straightforward. The fan comes with a pre-wired mains lead and a wall-mounting bracket. Fit the bracket, connect your 125mm ducting, run the lead to a socket, and you are done. G-Tools sell a matching PK K2601 carbon filter designed to work directly with this fan; the two together form a complete odour-control circuit without any adaptor rings or reducers.

The Prima Klima heritage behind this fan matters. The same unit has been sold under the Prima Klima badge for years and earned a strong reputation in the European growing market. The backward-curved impeller is the key design detail - it maintains airflow against the resistance of a loaded carbon filter better than a forward-curved blade, so rated performance figures stay closer to real-world figures.

Grower’s Note: When sizing any 125mm fan, account for carbon-filter resistance - a loaded filter can reduce effective airflow by 20-30%. Running this fan on high speed with a fresh filter gives you genuine margin. As the filter ages, the low-speed setting becomes less useful for odour control; that is a reliable sign it is time to replace the carbon. Keep ducting runs short and bends to a minimum to preserve as much of that 400 m³/h as possible.

Priced at £159, with free UK delivery.