What Is An ioniser, and Does It Matter?

What an ioniser actually does#

An ioniser emits charged ions that attach to airborne particles. The charged particles then settle out of the air, clinging to walls, soft furnishings, or a collection plate if the unit has one.

The particles leave the air, which is real. Where they land is the part the marketing tends to abbreviate: a charged particle on your curtains is not a particle in a filter, and dust that has moved house can move again.

The byproduct caveat#

Some ionisation produces ozone as a byproduct, and ozone is a lung irritant, EPA's guide is unambiguous about that. If a unit has an ioniser, it should be one you can switch off.

The sensory tell people describe, a sharp or metallic smell near the unit, is not a freshness signal. Treat it as a reason to open a window and reconsider the setting.

Does it matter?#

Partly, at best. Charging particles is not delivering cleaned air, and no CADR benefit for ionisation appears anywhere in EPA's published table. The figures that size a unit are still the dust, pollen and smoke CADR numbers.

A good purifier with a switchable ioniser is a fine purifier with a gimmick attached. A poor one with an ioniser is still a poor one, the feature does not change the arithmetic.

What to check on the box#

• Whether the ioniser can be switched off independently. If it cannot, the byproduct question has been answered for you.
• A published CADR. Ionisation adds no row to EPA's table and no number to the comparison.
• Where charged particles are meant to end up, a washable collection plate, or your soft furnishings.
• Whether ionisation is presented as a feature or smuggled in as a rating. Only one of those is a rating.