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Alen replacement filter

Alen BreatheSmart 45i / FLEX

Alen lists Essential (Pure) HEPA filter for 45i and FLEX for US BreatheSmart 45i, BreatheSmart FLEX. The Amazon action is a reference search without an approved retail item or pack.

Models listed by the manufacturer

  • BreatheSmart 45i
  • BreatheSmart FLEX

Models checked: US. Match the full code on your label.

Where is my model number?

Before you buy

  • Do not use B3, B7 or Classic BF35 filter codes for 45i/FLEX.
  • The attached pre-filter does not turn the replacement assembly into a four-pack; spare pre-filter packs have separate contents.
  • These manufacturer-listed US model codes do not approve another regional variant. The Amazon action is a reference search, without an approved product, seller or pack.
Find the complete model code
  1. Read the complete Alen model on the purifier label and retain every letter, digit and suffix.
  2. Match the label with one of the manufacturer-listed US codes on this page.
  3. Compare B4-Pure, components and quantity on the final merchant listing; the search does not approve the listed item or pack.
Filter and fitting details
  • Alen names B4-Pure for 45i Pure/Essential and explicitly states that BreatheSmart 45i and FLEX share filters.
  • Essential (Pure) is described as formerly B4 Pure. This variant stays separate from Fresh/Advanced and Odor/Ultimate.
  • The manufacturer FAQ states that the pre-filter comes attached, using black mesh and Velcro on the 45i filters.

Manufacturer sources

Documentation checked Oct 13, 2026 by Codex (manufacturer documentation). We have not physically tested these filters.

Alen filterB4-Pure
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