HEPA is the rare acronym with teeth: a true HEPA filter captures 99.97% of particles at 0.3 microns — the hardest size to catch — with higher efficiency either side of it.

What the standard means, what it doesn't, and how to buy-and-run one honestly.

Key Takeaways

  • True HEPA = 99.97% at 0.3 µm — the hardest particle size.
  • Gases and odours pass through; real carbon mass handles those.
  • Size by CADR for 4–5 bedroom air changes hourly.
  • 'HEPA-type' is a confession, not a standard.

What the Standard Means

The spec: 99.97% capture at 0.3 µm (the 'most penetrating particle size' — smaller AND larger particles are caught more easily, counterintuitively), achieved by fibre mats using impact, interception and diffusion physics rather than simple sieving. Marketing dialects to watch: 'HEPA-type' and 'HEPA-like' are confessions, not standards; 'True HEPA' or H13 ratings are the real thing.

What HEPA Catches and Misses

In scope: dust, pollen, mould spores, dander, smoke particles, bacteria-and-virus-laden aerosols — the particle world. Out of scope: GASES — VOCs, odours and NO2 sail through fibre mats entirely; that job belongs to activated-carbon stages (worthwhile when sized honestly — thin carbon sheets are decorative). The pairing explains combo units: HEPA for particles, real carbon mass for chemistry.

Sizing by CADR

The purchase maths: Clean Air Delivery Rate (CADR) against room size — the rough rule seeking 2/3 of the room's square-footage as smoke-CADR, or computing for 4–5 air changes hourly in bedrooms; undersized units running flat-out underperform right-sized units purring. Noise ratings decide real-world use: the quiet setting you'll actually run beats the turbo setting you won't.

Maintenance That Keeps It Honest

The upkeep contract: pre-filters rinsed monthly (they protect the HEPA's lifespan), HEPA elements replaced on schedule (6–12 months typical by use — a loaded filter restricts flow before it stops filtering), carbon stages replaced when odour-grab fades, and placement honoured (clear of walls and curtains, breathing-zone adjacent in bedrooms). A neglected purifier is furniture.

HEPA verdict: genuinely effective physics for the particle half of indoor air — bought by CADR, run quiet-and-constant, maintained like the appliance it is.

Frequently Asked Questions

Do HEPA purifiers really help allergies and asthma?

Trials show meaningful allergen-and-particle reductions with right-sized bedroom units — symptom improvements follow for many, as part of the wider exposure-reduction package.

Why does my purifier do nothing for cooking smells?

Smells are gas-phase chemistry — HEPA's fibres can't touch them. Ventilation and substantial activated carbon are the odour tools.

Can I run a purifier all night?

That's the intended use: quiet-setting continuous operation in the bedroom delivers the air-change arithmetic sleep deserves.

Daily Respiratory Support, One Spray at a Time

BreathiZen pairs mullein, ginger and organic lemon in a once-daily oral spray — ordered only through the official Breathizen website and backed by a 60-day money-back guarantee.

Visit the Official Order Page

Sources & Further Reading

Educational content only — not medical advice. Sources are general references on the topic, not studies of the BreathiZen formula.