Blue Signature SP4i Air Purifier: Trusted Review & Specs

The Blue Signature Large (SP4i) is truly the best of everything in the current home air purifier world. It’s got the best performance per watt, the highest CADR numbers in its class, the most comprehensive filtration, and the smartest features. You’ll pay for all of that but, if you’re determined to get an air purifier and want the absolute apex device, this is clearly the unit for you. Let’s talk more in our Blue Signature SP4i review.

Blue Signature Large SP4i ranks S- in our air purifier ranking list. We give the biggest and most thorough database of air purifier reviews in the world.

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Blueair introduces the Blue Signature series – as a high-end Blue Pure Max successor, selling the brand’s most deliberate departure from conventional air purifier design: a cylindrical, furniture-grade lineup built to double as a functioning side table while delivering great performance. Today, we will talk about the best one, in the Blue Signature SP4i review.

Other Blueair’s Air Purifier Reviews:

Blue Signature Large SP4i Price

Ahead of launch, we ran an informal poll on which new Blueair air purifier people wanted. The Blue Signature Large SP4i was the clear favorite – and by a wide margin. It’s not just the table cylindrical design or the promise of industry-leading performance, it seems current air purifier buyers want all the features that come with Blueair’s premium unit.

And good news: this is the ultimate home air purifier.

It’s no more powerful than the Blue Pure 211i Max that costs a lot cheaper, but the Signature series is more for its design than its p/p ratio. Still, the Blue Signature Large SP4i costs around $449, meaning it’s a $149 jump from the smaller Blue Signature SP3i. Yes, that’s the price to buy a new Blue Pure 511i Max.

Blueair seems to be competing more directly with the Levoit EverestAir, Coway Airmega 450, and AeraMax SE. These are top-tier air purifiers that people consider at this price range. With similar performance and smart features, the Blue Signature Large stands out by being newer, more stylish, and overall better.

More good news, you can get one from our Breathe Quality deal, and the Blue Signature SP4i is only $344 for a limited time, which is 23% OFF.

Related post: Best air purifier 2026.

Blue Signature Large SP4i Design and Size

At a glance, and aside from the lovely new Nordic Fog finish, the Blue Signature Large SP4i could be mistaken for a designer side table. It’s that convincing. Still, there are some subtle differences.

At 16.75 × 14.5 × 14.5 inches, the Blue Signature Large is slightly shorter and wider than a typical tower purifier, and a touch wider. None of this is distracting when you look at or live with the unit; perhaps that’s because, at 13 pounds, it’s light enough to carry between rooms using its integrated handles. This is a very convenient addition compared to the Blue Pure 211i Max, which doesn’t have a handle at all.

With the Blue Signature SP4i (and the Blue Signature SP3i), you get Blueair’s premium material experience; which means a smooth ABS housing, with a stretch-knit fabric pre-filter wrapping the exterior front and back.

The flat top surface is protected by a solid lid that can support light objects like books or mugs, which should hold up well in daily use (we did not load or purposely stress the lid to test it, but in general use it showed the top of the unit is clearly stable enough for resting items, where the fabric sides are more delicate). The top control panel features a motion-activated display that only lights up when it detects hand movement.

Even though the cylindrical form is similar to the older Blue Pure series, the base is now slightly larger to better support the weight. You can add wooden legs or a disc to increase the height of the Blue Signature Large, but keep in mind that these accessories start at $69, so they aren’t cheap.

Related post: Best air purifiers for bedroom.

Blue Signature Large SP4i Filters

We check the performance of one air purifiers based on its air filters’ quality and material, as well as the number of air filter types in the testing device. We have the same 3-stage air cleaning system for the Blue Signature Large.

1. Pre-filter – It’s worth noting that the fabric pre-filter of the Blue Signature Large is outside the air purifier. This is one great advantage of this pre-filter, because you can easily check its status and vacuum or wipe the contaminants out immediately.
2. Particle filter – Instead of using a True HEPA filter, the Blue Signature Large runs a polypropylene fiber filter to help capture 99.97% of all allergens as small as 0.3 microns like dust, dust mites, pet dander, pollen and fungi (HEPASilent technology).
3. Activated Carbon filter – The Activated Carbon filter is added inside the Particle filter and effective against smoke, odors, gases and VOCs. It uses enzymes and minerals to break down odors molecules, instead of storing them.

From the smaller Blue Signature SP3i, Blueair uses the new clasp air filter for the Signature series, and the Blue Signature Large isn’t an exception. The clasp design improves the seal integrity and reduces air bypass inside the purifier.

The Blue Signature Large still uses the signature HEPASilent technology, which combines mechanical filtration with electrostatic charges. This helps improve the efficiency of the main filter without increasing fan power, thus reducing the overall noise level. It is the very core of Blueair’s filtration system.

The Blue Signature Large also features a newer carbon filter. Using bio-based enzymes and minerals, mostly zeolites, it offers better efficiency against common VOCs like acetaldehyde (CH₃CHO). This type of material is typically used in high-end air purifiers, and even in a smaller amount, it gives the Blue Signature Large slightly better performance than a standard carbon filter.

In the mid-range test at closed space of 400 square feet, the Blue Signature Large is working amazing, as it can clean 99.99% of all particles down to 0.3 microns in just 1 hour. The performance is very close to the Airmega 450, and is far better than the Airmega 350 and AeraMax SE.

Preview of 400 sq ft efficiency widget — 6 confirmed models shown, InvisibleMist pending clarification

We will need the new filter for the

Related post: Best air purifiers for allergies.

Blue Signature Large SP4i Room Coverage

We have another AHAM-verified air purifier from Blueair, and the Blue Signature Large will cover up to 705 square feet. Such performance is even bigger than the Blueair HealthProtect 7770i that we loved in the past.

The ACH of the Blue Signature Large SP4i is 5X. For an AHAM-verified unit, the air purifier exchanges air 5 times per hour in its suggested room size.

The CADR of the Blue Signature Large SP4i is 434 Dust/ 455 Smoke/ 450 Pollen (cfm). This is perhaps one of the highest CADR ratings tested by AHAM.

Related post: Best large room air purifiers.

Blue Signature Large SP4i Sound

As large as the Blue Signature Large is, its noise level can be as low as 23 decibels (dB) on the lowest fan speed. This makes it suitable for bedrooms, as the noise is comparable to the sound of rustling leaves.

The Blue Signature Large runs a bit louder at its highest fan speed, reaching 58 decibels. That is roughly equivalent to the noise level of a normal office conversation.

Related post: Best air purifiers for baby.

Blue Signature Large SP4i Power Consumption

One of our most FAQs is “Do air purifiers use a lot of energy?” An air purifier is meant to run for a long time to be efficient, that’s why many air purifier brands consider the energy-saving standard, mostly in the rate of Energy Star, is one important selling point.

The Blue Signature Large SP4i is also an Energy Star air purifier, and it is one of the best energy-saving air purifiers, with its power consumption at only 40 watts. It is even better than the Blue Pure 211i Max that we praised not long ago.

Running the Blue Signature Large everyday at least 8 hours, you only need to pay $17.53 each year.

Related post: Best air purifiers for pets.

Blue Signature Large SP4i Additional Features

For a long time, the mid-range to high-end air purifier market was dominated by non-smart devices. That is now a thing of the past, thanks to Blueair’s continuous innovation since the very old Classic series. The Blue Signature Large SP4i is now a fully smart device with built-in Wi-Fi capability. You can use the app to remotely control the air purifier, set it to automatically turn on when you are nearby, or enable the child lock for the display.

Moreover, the air purifier has both dust and smoke sensors, and by enabling Auto Mode, you can live without worrying about indoor air quality. Auto Mode automatically adjusts the fan power to respond to real-time pollutants, and the Blue Signature Large reacts almost immediately to airborne particles in the environment.

Modern Blueair air purifiers now feature the new RealTrack filter life alert, which predicts filter life based on surrounding pollutants and the most frequently used fan speed. It is an AI-based prediction system that can be further improved through firmware updates downloaded from the app.

Related posts:

1, Best air purifiers for smoke.

2, Best air purifiers for dust.

3, Best air purifiers for mold.

Blue Signature Large SP4i Customer Service

As one of the best air purifier brands, Blueair focuses strongly on customer service. With a lot of local stores and dedicated support via phone and email, you are guaranteed to reach its customer service as soon as possible.

If you need to find a local store of Blueair anywhere in the world, you can use the store locator function on its website. To reach customer service, you can choose between calling 888-258-3247 or emailing info@blueair.com. Customer service is available for you from Monday to Friday, with the exception of U.S. holidays.

Remember only one thing: you need to complete the Product Registration form within 60 days of purchase or register through the Blueair Friend mobile app to secure the 5-year warranty. Otherwise, you only benefit from a 1-year warranty. Moreover, do not attempt to bring the air purifier outside of the United States or Canada, or your warranty will be void immediately. All Blueair warranties are non-transferable.

Blueair air purifiers from the Blue family have only a 2-year warranty from the date of purchase (with valid proof of purchase). One quick reminder: Blueair doesn’t cover warranties from third-party sellers, so buying from Breathe Quality’s deals is highly recommended.

Our verdict

The Blue Signature Large shares the same performance as the Blue Pure 211i Max, but at a price that is $100 higher. However, you get a more energy-efficient air purifier, a better carbon filter for odor control, and a design that works as an attractive piece of furniture.