Blueair 511, 3250i, 3350i, 3450i: What's the Signature series?

If you've bought a Blueair purifier from us before, you might have noticed some names moving around in the shop. The Blue Max 3250i, 3350i and 3450i are all showing as sold out on our site at the moment, and Blueair's launched a new Blue Signature range alongside the rest of the lineup: the Signature series: SP1i (Small), SP3i (Medium) and SP4i (Large).

To be clear, Blueair hasn't announced the older models as discontinued, and some of them are still listed at other UK retailers, so this isn't an official phase-out. But the Signature range is clearly where the new development is going, and if the model you'd normally buy is out of stock with us, it's worth knowing what the nearest current equivalent is. So here's the plain version of how the two ranges line up.

Why the change

Blueair's old numbered range had been through several generations of small tweaks, but the Signature series is a proper redesign rather than a refresh. The units now double as side tables, with wooden legs and chrome ring bases available if you want them, so they don't have to hide in a corner anymore. Inside, there's 7-stage filtration with something Blueair calls OdorFence, which they claim removes odours up to 10 times more effectively than before, on top of the usual 99.97% particle capture down to 0.1 microns. There's also a proper VOC sensor now, which the old PM2.5-only sensors couldn't do, and the filters are rated to last roughly twice as long thanks to a new filter design. The display's changed too, it's a motion-activated touchscreen rather than the old button and LED ring.

The bit that matters most if you're comparing models, though, is raw power. Once you convert the CADR figures to the same units (more on that below), every Signature model is moving noticeably more air per hour than the old models.

Which new model replaces which old one

Blueair hasn't put out an official chart saying “this replaces that”, so what follows is our own read based on comparing room size coverage, CADR and price between the old and new ranges. It isn't an official Blueair statement.

One thing to flag before the table: the old Blue Max/Pure range publishes CADR in m³/h, but the new Signature range publishes it in CFM. We've converted the Signature figures to m³/h below (1 CFM is roughly 1.7 m³/h) so they're actually comparable. If you're looking at spec sheets yourself, do that conversion first. Compare the raw numbers as printed and you'll wrongly conclude the new units are barely better.

Old model	Old room size (AHAM)	CADR	New model	New room size (AHAM)	New CADR (converted to m³/h)
Blue Pure 511	16m²	191 m³/h	Signature SP1i (Small)	23m²	304 m³/h
Blue Max 3250i	20m²	239 m³/h	Signature SP1i (Small)	23m²	304 m³/h
Blue Max 3350i	36m²	425 m³/h	Signature SP3i (Medium)	46m²	561 m³/h
Blue Max 3450i	43m²	510 m³/h	Signature SP4i (Large)	65m²	773 m³/h

The 511 and 3250i look to have been consolidated into one model. Blueair used to sell two small bedroom purifiers at different price points, and now there's just the SP1i covering that ground. Even at the bottom of its CADR range it moves noticeably more air than either predecessor, so if you had a 511 or a 3250i, the SP1i is the natural upgrade. 

The power jump is very noticeable, comparing the raw numbers side by side, the SP4i is moving roughly 45 to 50% more air per hour than the 3450i, and the SP3i is moving 25 to 30% more than the 3350i.

Pricing has moved up a bit across the board. The SP1i at £149.99 sits above the old 511 (£99) but below the 3250i (£169). The SP3i at £269 sits above the 3350i (£239). The SP4i at £369 sits above the 3450i (£299). You're paying a little more in most cases but for a genuinely more capable, better specced unit.

What this means if you already own an older model

Your existing 511, 3250i, 3350i or 3450i isn't going anywhere. It'll keep working fine, and replacement filters are still available and will be for years to come. This is purely about what's available to buy new. The Signature range is the direct upgrade path, with a real jump in filtration, sensing and how much air it actually moves in a really nice looking unit.

Which one should you buy

If you're after something for a bedroom, home office or nursery, and previously would have gone for a 511 or 3250i, the SP1i (Small) is the like-for-like upgrade. For living rooms and open-plan kitchen-diners, where a 3350i would have done the job, the SP3i (Medium) is the closest match. And for large open-plan spaces or XL living rooms, or if you just want the most powerful compact unit Blueair makes, the SP4i (Large) is the perfect choice.