A cheap DIY device that rivals expensive purifiers attracts scepticism. Some of it is fair; much of it isn't. Here are the common claims, checked.
681 m³/h CADR, MERV-13, under 35 dB — powerful whole-home clean air — no proprietary lock-in, ships from the UK.
Check price →Use code CORSI10 for 10% off at checkout."It's just a fan blowing air around"
No — the air is pulled through four or five MERV-13 filters that capture around 93 per cent of airborne particles. The fan provides the airflow; the filters do the cleaning. Together they deliver a high clean-air rate, which is measurable with a particle counter.
"DIY can't match a real HEPA purifier"
On per-pass capture, HEPA is higher. On clean-air delivery — what actually clears a room — a CR box's high airflow often wins, because HEPA's dense media throttles airflow. Independent testing has repeatedly shown CR boxes rivalling far pricier units. See the research.
"It's too loud to actually use"
A box fan is louder than an engineered purifier, true — but a shroud, a lower speed and a soft surface make it liveable, and a ready kit runs under 35 dB if noise is a dealbreaker.
"MERV-13 doesn't catch small particles"
It does — through diffusion and interception, not just sieving, MERV-13 captures particles far smaller than its fibres, including PM2.5. It is the grade public-health bodies recommended for indoor filtration.
"It's a fire risk"
Used sensibly — a modern fused-plug fan, filters not blocking airflow, kept clear of fabrics — a CR box is no more a risk than the fan alone. Don't cover the intake or run a damaged fan.