The catch
Blueair Blue Signature Large
If you want a fully mechanical air path, look elsewhere, since HEPASilent relies on an ionization stage that is always on.
Side by side
Blueair Blue Signature vs Coway Airmega 400: Coway stays mechanical and needs no app setup
Quick verdict
The Blue Signature is the pick if you want quieter, faster smart operation. The Airmega 400 is the pick for a mechanical True HEPA system that has no app and no ionizer in the air path.
Before you buy
Why, and what it costs you
The catch
Coway Airmega 400
You won't get a Wi-Fi app, scheduling or a detailed air-quality history.
Blueair Blue Signature Large
- Why pick it
- A higher smoke CADR and a less bulky look are what you're after.
- App control, scheduling and detailed automatic operation are important to you.
- The catch
- If you want a fully mechanical air path, look elsewhere, since HEPASilent relies on an ionization stage that is always on.
Coway Airmega 400
- Why pick it
- You're looking for certified HEPA filtration with no ionizer.
- Dual washable prefilters appeal to you for a room full of pets.
- The catch
- You won't get a Wi-Fi app, scheduling or a detailed air-quality history.
The Airmega 400 photo shows Graphite, while the Amazon listing selects White. Its purchase link is paused while the exact finish is verified.
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What this page compares
Two large-room leaders go head to head on particle airflow, ionization, controls, filter layout and ownership.
This one comes down to particle airflow and ionization first, then to the limits of your own setup.
Day to day
How each one fits your routine
A tall living room reshuffles the maximum-speed shortlist
Take a 600-square-foot room with a ten-foot ceiling and a five-air-change planning target. That works out to 500 CFM. Signature's 455 smoke CADR falls short of it and so does Airmega 400's 328, and that is before either is turned down for sleep. If that exact room and target are fixed, neither is enough as a single unit. For a smaller room, work out its volume first and decide from that, instead of comparing the biggest advertised square-foot number.
Where this comes from
600 times 10 times 5, divided by 60, comes to 500 CFM. The figure relies on smoke CADR at rated conditions. It is not airflow at minimum sound and not a guaranteed result in a real room.
A furniture-style placement still has to leave room for servicing filters
Airmega 400 pulls air in from two sides and carries two washable prefilters, so a narrow recess that blocks one side defeats the placement plan. Signature's smaller square footprint may be simpler to put in the open, yet it still needs intake clearance and filter access. Go with Coway if its broad two-sided service area fits your space. Go with Signature if its smaller body is the practical way to keep the purifier out of a cramped gap.
Where this comes from
Listed footprints are about 14.8 inches square for Coway and 13 inches square for Signature. Body dimensions are not the same as the clearances needed to operate, and neither unit should be treated as ready for cabinetry.
Which one fits
Pick the situations that sound like you
I sleep very lightly
Blueair Blue Signature Large lists “App, sensor and Auto mode” for controls, while Coway Airmega 400 lists “Sensor, Auto and Eco. No app”. This shapes setup and day-to-day use more than the core physical job.
- Blueair Blue Signature Large
- Better fit
- Coway Airmega 400
- Good
I'll look at air quality on my phone
The app shows air quality or history and lets you run the purifier remotely.
- Blueair Blue Signature Large
- Better fit
- Coway Airmega 400
- Depends
My ceilings run higher than normal
Extra ceiling height raises the room volume, and its verified airflow leaves more headroom to handle that.
- Blueair Blue Signature Large
- Better fit
- Coway Airmega 400
- Good
I need the air cleaned up fast
In a room of the right size, its high verified pollutant CADR leaves extra cleaning headroom.
- Blueair Blue Signature Large
- Better fit
- Coway Airmega 400
- Good
It will be on all day
Running it around the clock is more reasonable given its documented power use and airflow.
- Blueair Blue Signature Large
- Better fit
- Coway Airmega 400
- Good
I'd rather swap filters less often
Blueair Blue Signature Large lists “Single wraparound filter” for filter layout, while Coway Airmega 400 lists “Two Max2 filters and two prefilters”. For filter layout, this shows what the treatment path is designed to catch or reduce, and the upkeep it needs.
- Blueair Blue Signature Large
- Better fit
- Coway Airmega 400
- Good
Plug in your numbers
Can either purifier keep up with your room?
This checks hard limits only. Personal preferences are left out of the math.
Blueair Blue Signature Large
Works with your numbers455 CFM of verified clean-air delivery works out to about 11.4 air changes per hour in this room. Hitting the 5 ACH target takes 200 CFM.
Coway Airmega 400
Works with your numbers328 CFM of verified clean-air delivery works out to about 8.2 air changes per hour in this room. Hitting the 5 ACH target takes 200 CFM.
This uses each model’s pollutant-specific CADR at top speed and a target of five air changes per hour. Quieter settings clean less air. Raw airflow and one-change coverage claims are never swapped in.
Option A
Blueair, SP4i
Blue Signature Large
This refined purifier is aimed at large rooms and pairs unusually high verified airflow with restrained sound and a responsive app that handles automation.
- Best for
- A higher smoke CADR and a less bulky look are what you're after.
Facts we checked
- Particle airflow: 455-CFM smoke CADR
- Ionization: Always-on HEPASilent stage
- Controls: App, sensor and Auto mode
- Filter layout: Single wraparound filter
Option B
Coway, AP-2015F
Airmega 400
Wide and high in airflow, this purifier has dual filters, two washable prefilters and straightforward automatic controls, with no app involved.
- Best for
- You're looking for certified HEPA filtration with no ionizer.
Facts we checked
- Particle airflow: 328-CFM smoke CADR
- Ionization: No ionizer
- Controls: Sensor, Auto and Eco. No app
- Filter layout: Two Max2 filters and two prefilters
The Airmega 400 photo shows Graphite, while the Amazon listing selects White. Its purchase link is paused while the exact finish is verified.
Spec by spec
Where they really differ
| Spec | Blueair Blue Signature Large | Coway Airmega 400 | In practice |
|---|---|---|---|
| Particle airflow | 455-CFM smoke CADR | 328-CFM smoke CADR | Higher published output is useful only if your room, surface or workload calls for the extra headroom. It does not, by itself, prove better results. |
| Ionization | Always-on HEPASilent stage | No ionizer | For ionization, this shows what the treatment path is designed to catch or reduce, and the upkeep it needs. |
| Controls | App, sensor and Auto mode | Sensor, Auto and Eco. No app | Setup and everyday use depend on it more than the core physical job does. |
| Filter layout | Single wraparound filter | Two Max2 filters and two prefilters | For filter layout, this shows what the treatment path is designed to catch or reduce, and the upkeep it needs. |
Trade-offs
What each pick costs you
With Blueair Blue Signature Large
- Its thin carbon layer handles everyday odors, but it isn't built for steady VOC or solvent exposure.
With Coway Airmega 400
- The wide body takes up a lot of floor space and needs room to breathe on both intake sides.
By the numbers
What the data shows
What we found across the air purifiers we compare, plus the checked facts behind each finding.
Show the facts and the math
| Product | Needs it meets | Facts we checked | Sources |
|---|---|---|---|
| Blueair Blue Signature Large |
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| Coway Airmega 400 |
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Ready to buy
See today’s price and what owners say
Open either model on Amazon for the current price, customer reviews and delivery options.
Blueair Blue Signature Large
A higher smoke CADR and a less bulky look are what you're after.
See price & reviews on AmazonCoway Airmega 400
You're looking for certified HEPA filtration with no ionizer.
The Airmega 400 photo shows Graphite, while the Amazon listing selects White. Its purchase link is paused while the exact finish is verified.
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