HEPA is a standard for filters that capture very small particles. Product pages often use the term loosely, so it helps to know what to look for.
What HEPA means
A true HEPA filter is designed to capture at least 99.97% of particles at 0.3 microns under standard test conditions. Some products use similar names that do not meet that standard, so read the specification.
Multi-stage filtration
Many purifiers combine a pre-filter for larger particles, a main filter and sometimes an activated carbon layer for odours. Check how many stages a model has and what each does.
Filter life and replacement
Filters are consumables. Find the recommended replacement interval and the price of replacement filters before you buy.
Avoid unproven claims
Be cautious of products that promise to cure or prevent illness. A purifier filters air that passes through it; check the manufacturer's stated specifications and any independent certifications.
Quick checklist
- Is the filter true HEPA?
- How many stages?
- How often are filters replaced and at what cost?
