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Alen · air purifier filter

Alen 45i & FLEX Filter, Essential (Pure) (B4-Pure)

BreatheSmart 45i & FLEX HEPA Filter, Essential (Pure). Part B4-Pure. Replace every 6-12 months. Fits 2 models.

Buy 45i & FLEX Filter, Essential (Pure) on AmazonManufacturer page

Opens an Amazon search for Alen 45i & FLEX Filter, Essential (Pure) B4-Pure. Check the listing says B4-Pure.

Fits these models

Part numbers

Genuine part
B4-Pure
Also listed as
FL40-Pure, F10016
How often
Replace every 6-12 months
What is in it
Prefilter (attached); Medical-grade HEPA

Sources

  • Which filter fits alen.com Maker's own page checked Oct 1, 2026
    BreatheSmart 45i & FLEX HEPA Filter ... Q: Will this filter also fit in Breathsmart Flex unit? A: Yes. The BreatheSmart 45i and BreatheSmart FLEX share the same filters.
  • How many web.archive.org Maker's archived page checked Oct 1, 2026
    Page for the BreatheSmart 45i (per its URL): Remove the used filter by pulling out on the ribbon loop ... Take the new filter out of the plastic bag and insert it into the purifier with the ribbon loop facing outward (archive.org copy of 2025-10-09)
  • How often alen.com Maker's own page checked Oct 1, 2026
    Purifier includes filter rated for: 6-12 months
  • What's in it alen.com Maker's own page checked Oct 1, 2026
    All of our filters come with a Prefilter attached. On the BreatheSmart 45i filters, the prefilter is the black-mesh attachment with Velcro on the front of the filter.
  • Other genuine options alen.com Maker's own page checked Oct 1, 2026
    (Formerly B4 Fresh) ... (Formerly B4 Odor)
Show all 10 sources

Which filter fits

  1. alen.com Maker's own page checked Oct 1, 2026
    BreatheSmart 45i & FLEX HEPA Filter ... Q: Will this filter also fit in Breathsmart Flex unit? A: Yes. The BreatheSmart 45i and BreatheSmart FLEX share the same filters.
  2. alen.com Maker's own page checked Oct 1, 2026
    Our entry-level filter. Features a medical-grade HEPA filter that captures 99.9% of airborne dust, viruses, and allergens. (Formerly B4 Pure)
  3. alen.com Maker's own page checked Oct 1, 2026
    BreatheSmart 45i & FLEX HEPA Filter variants: Essential (Pure) F10016; Advanced (Fresh) F10017; Ultimate (Odor) F10014
  4. web.archive.org Maker's archived page checked Oct 1, 2026
    4 Filter options: Pure, Fresh, Odor, and VOC/Smoke | BreatheSmart FLEX & 45i filters are compatible (archive.org copy of support.alen.com, 2025-09-05; live page returns 403)
  5. web.archive.org Maker's archived page checked Oct 1, 2026
    Breathesmart FLEX HEPA Air Filter: B4-Pure / FL40-Pure (archive.org copy of 2023-06-03)

How many

  1. web.archive.org Maker's archived page checked Oct 1, 2026
    Page for the BreatheSmart 45i (per its URL): Remove the used filter by pulling out on the ribbon loop ... Take the new filter out of the plastic bag and insert it into the purifier with the ribbon loop facing outward (archive.org copy of 2025-10-09)
  2. web.archive.org Maker's archived page checked Oct 1, 2026
    Page for the BreatheSmart FLEX (per its URL): Remove the used filter by pulling out on the pull strings ... insert it into the air cleaner with the pull strings facing outward (archive.org copy of 2025-08-13; live page returns 403)

How often

  1. alen.com Maker's own page checked Oct 1, 2026
    Purifier includes filter rated for: 6-12 months

What's in it

  1. alen.com Maker's own page checked Oct 1, 2026
    All of our filters come with a Prefilter attached. On the BreatheSmart 45i filters, the prefilter is the black-mesh attachment with Velcro on the front of the filter.

Other genuine options

  1. alen.com Maker's own page checked Oct 1, 2026
    (Formerly B4 Fresh) ... (Formerly B4 Odor)