Blueair 211i Max vs 311i Max

Choose the Blueair Blue Pure 311i Max for a bedroom or office that fits its current 439 sq ft recommendation; choose the 211i Max for a larger room, up to the maker's 674 sq ft recommendation. Both figures use 4.8 air changes per hour (ACH); the 211i Max offers more published airflow, while the 311i Max takes less space. The catch is naming: 311i Max and 311i+ Max are separate products, and an older “Blue Pure 211” listing is not enough to identify the 211i Max. 211i Max specifications, 311i Max specifications.

Quick picks

• Smaller room, less cabinet to accommodate: choose the 311i Max if its room-size basis fits your space.
• Larger living area, more published airflow: choose the 211i Max if you can accommodate its larger cabinet.
• Shopping for an existing purifier: read its label first. Choose the replacement filter for that exact name, including Max and any + sign.

For other brands, see our best air purifiers and quiet air purifiers for bedrooms.

211i Max vs 311i Max comparison

Official US documentation checked November 2, 2026. Room size, noise and power are manufacturer claims. The current product-page technical tables supply the figures in this table; the manuals supply sensor and control details.

Sources: 211i Max page, 311i Max page, 211i Max manual, 311i Max manual.

• Blue Pure 211i Max435cfm
• Blue Pure 311i Max283cfm

Source: Blueair US product-page technical tables, checked November 2, 2026; not Night-mode airflow

Choose the 211i Max for the larger room

The 211i Max is our pick when airflow is the reason to step up. Its current smoke CADR is 435 cfm, against 283 cfm for the 311i Max. Its sensors also report PM1, PM2.5 and PM10, where the smaller model's manual specifies PM2.5. Specifications, manual.

The trade-off is physical: 14.4 in wide and deep, 22.7 in tall and 16.2 lb. Measure its intended spot. Its 674 sq ft at 4.8 ACH rating is the relevant sizing figure here, not the much larger 3,235 sq ft in one hour headline on the same page. The cleaning frequencies differ. Blueair's table and room-size FAQ.

Check price on Amazon

Choose the 311i Max for a smaller bedroom or office

At 12.5 × 12.5 in across the base and 7.8 lb, it is smaller and lighter than the 211i Max. You still get Auto and Night modes, plus app schedules and filter tracking. Blueair's current page.

Its manual describes straightforward On/Standby and Fan Speed buttons. Night mode uses the lowest fan speed and fully dimmed lights; Auto adjusts speed according to PM2.5 readings. 311i Max manual.

Choose the 211i Max if your room exceeds the smaller model's recommendation. The published noise ranges do not establish which is quieter at matched airflow.

See the exact 311i Max at Blueair.

Which room-size figure should you trust?

Measure your room's length and width, multiply them for floor area, then compare the technical-table recommendations. CADR stands for clean air delivery rate; we compare the same smoke-particle rating for both machines. Keep older ratings separate. AHAM's sizing FAQ. Blueair says it updated CADR and room-size values to meet new DOE standards and that packaging may differ during the transition. Its website still conflicts with itself. Blueair's update note.

For the 311i Max, the technical table says 439 sq ft / 283 cfm smoke CADR, the page title says 465 sq ft, and raw page metadata still says 387 sq ft. The benefits text also says 2,207 sq ft in one hour, while the FAQ says 2,107 sq ft in one hour. We use neither one-hour claim to choose between these machines. 311i Max page.

There is a dated independent reference, too. AHAM's October 2023 directory lists 250 cfm smoke CADR / 387 sq ft for model 3332111100, and 410 cfm / 635 sq ft for 3613111100, named “Pure Blue 211i Max” there. These historical entries do not independently confirm today's manufacturer figures. AHAM's current sizing FAQ also specifies 4.8 air changes per hour. AHAM directory, model listings and sizing explanation.

Near the smaller model's limit, we would choose the larger model if it fits. Do not assume either full-capacity room rating applies in Night mode: both manuals describe Night as the lowest fan speed. For sizing terms, see the room-size section of our purifier guide.

Name map: 211, 211+, 211i Max and 311i+ Max

Sources: AHAM's older model names, separate 311i+ Max manual, and the manuals linked above.

Placement, noise and app use

Both have a top outlet; their manuals say not to block the inlet or outlet or place objects on top or directly against the unit. Allow usable space around the cabinet; use a floor or stable surface. 211i Max manual, 311i Max manual.

The claimed sound ranges are 23–53 dB and 23–50 dB, respectively. Both manuals provide indicator-brightness adjustment, and both describe Night mode as the lowest speed with dimmed lights. The matching minimum claims do not establish equal-airflow quietness. 211i Max specifications, 311i Max specifications.

Both work through their local controls. For remote control and filter-use monitoring, their manuals require a Blueair account, 2.4 GHz Wi-Fi and Bluetooth for initial pairing. Both pages also describe app schedules and Welcome Home activation.

Filters, fabric sleeves and what comes in the box

Both purifier pages list an installed Particle & Carbon main filter and a fabric pre-filter. Blueair describes HEPASilent as combined mechanical and electrostatic filtration. Its main-filter choices include Particle & Carbon, SmokeBlock and AllergenBlock; choose the exact purifier's version of whichever type you want. 211i Max, 311i Max.

• 211i Max replacement: use Blueair's 211i Max Particle + Carbon filter. Its compatibility FAQ names only the 211i Max.
• 311i Max replacement: Blueair's 311i Max Particle + Carbon filter page conflicts with itself: its heading and “Designed for” say 311i Max, but its compatibility FAQ says 311i+. Ask Blueair to confirm the exact filter before ordering; do not infer interchangeability.

The 211i Max manual documents a transition from pull-over to wrap-around main filters, saying both designs fit the unit. Follow the instructions for the design you receive. The manual also explicitly says the main filter is not washable. Both manuals tell you to vacuum the fabric pre-filter with a soft brush, wash according to its label when needed, and hang it to dry. 211i Max maintenance instructions, 311i Max care instructions.

The 311i Max manual gives 6–9 months for replacement depending on use and air conditions. Its filter page says 6 month filter lifetime in one block and up to 9 months in its FAQ. Follow the purifier's indicator; a subscription's shipping interval is separate. 311i Max manual, conflicting filter-life statements.

• Yes: Match the full purifier name on its label to the filter's compatibility statement
• Yes: Keep the fabric pre-filter and main filter separate
• No: Do not assume 311i Max and 311i+ Max filters are interchangeable
• Partly: A filter subscription means recurring delivery; check initial bundle contents separately

Before holiday checkout

Both purifier box lists include installed filters; check an extra-filter bundle and recurring deliveries separately.

1. 1

   Identify the machine

   Read the full model name, including i, Max and any plus sign; compare it with the name map above.

2. 2

   Choose the room-size basis

   Use the current technical-table recommendation at 4.8 ACH; keep one-hour coverage and older packaging figures separate.

3. 3

   Read the contents and delivery terms

   Confirm the purifier, installed filters, any extra filter, selected filter type and whether future deliveries are recurring.

How we choose

We researched official specifications and manuals, without physical testing. We prioritize consistent room sizing, smoke CADR, dimensions, controls and filter compatibility. We keep the historical AHAM directory separate from current manufacturer figures and make no measured quietness verdict. Read our research method.

Verdict

Choose the 311i Max when its current room-size recommendation fits and you value the smaller cabinet. Choose the 211i Max for the larger space or more published airflow. Before buying either, match the complete model name, confirm the installed and extra filters, and check whether you selected recurring delivery.

Sources

Checked November 2, 2026: Blueair's US 211i Max and 311i Max product pages; 211i Max manual and 311i Max manual; the filter pages linked above; and the October 2023 AHAM directory, used only as a historical reference.