How often to replace an air purifier filter in NZ: a practical schedule
How often to replace an air purifier filter in NZ: a practical schedule
Quick answer: Most air purifiers need a filter change every 3 to 12 months, depending on the filter type and how hard it is working. As a starting point, replace activated carbon filters every 3 to 6 months, HEPA filters every 6 to 12 months, and wash reusable pre-filters every 2 to 4 weeks. If you live near busy roads, use a wood burner, have pets, or deal with smoke, you may need to replace sooner.
Knowing when to replace an air purifier filter is one of the easiest ways to keep your air purifier performing properly. In New Zealand, winter wood smoke, damp homes, and pollen seasons can load filters faster than you expect. In this guide we share a simple replacement schedule, the signs your filter is done, and how to make replacements cheaper and easier.
If you need a replacement or want to stock up, browse our air purifier collection. If you use a Therapy Air Ion unit, you can also check the Therapy Air Ion filter set.
Why filter replacement matters
Filters are the working engine of an air purifier. As they fill with particles and odours, airflow drops and the unit has to work harder. That can mean noisier operation, less cleaning performance, and higher running costs. Replacing on time keeps filtration efficient and helps the fan motor avoid unnecessary strain.
Typical air purifier filter replacement intervals
There is no single perfect schedule because every home is different. Use the ranges below as your baseline, then adjust based on your conditions and what you see on the filter.
Pre-filter (often reusable)
- Clean: every 2 to 4 weeks
- Replace: when it is damaged, warped, or will not come clean
Pre-filters catch larger dust and hair. Keeping them clean can extend the life of your main filter and keep airflow strong.
HEPA filter
- Replace: about every 6 to 12 months
HEPA filters trap fine particles such as pollen, smoke, and dust. Over time the fibres load up and airflow drops. If you have a compatible unit, you may want to keep a spare HEPA option on hand such as the HEPA filter for Therapy Air Ion.
Activated carbon filter
- Replace: about every 3 to 6 months
Carbon filters are designed for odours and gases. Once the carbon is saturated, it can stop removing smells even if it looks fairly clean. For smoke and cooking odours, a carbon option such as the activated carbon filter for Therapy Air Ion is often the piece that needs the most frequent replacement.
Combo filters (HEPA plus carbon)
- Replace: about every 6 to 12 months, or sooner if odour control drops
What makes filters wear out faster in NZ homes?
- Winter wood smoke: higher particle load can shorten HEPA life
- Roadside or urban traffic: more soot and fine dust
- Pets: hair and dander load pre-filters quickly
- Pollen season: spring and summer can spike filter loading
- Damp and mould-prone spaces: filters can clog faster and smell sooner
- Renovations: plaster dust can overwhelm filters fast
Signs it is time to replace your air purifier filter
- your purifier is louder than normal at the same setting
- airflow feels weaker at the outlet
- odours return quickly, especially cooking or smoke smells
- the filter looks grey, clogged, or visibly loaded
- you see a filter indicator light, app alert, or maintenance prompt
One simple check: hold the HEPA filter up to light. If very little light passes through compared with a new filter, it is likely time to replace.
How to replace an air purifier filter
- Turn off and unplug the unit.
- Open the filter cover and remove the old filters.
- Vacuum loose dust from the pre-filter area, if your manual allows it.
- Install the new filters in the correct order (usually pre-filter, carbon, then HEPA).
- Close the cover firmly and reset the filter indicator in the app or control panel.
Tip: set a calendar reminder for your next change based on the schedule in this article, then adjust after you see how quickly your filters load in your home.
Can you clean a HEPA or carbon filter instead of replacing?
Pre-filters are often washable or vacuumable, but most HEPA and carbon filters are designed to be replaced. Vacuuming a HEPA can damage fibres or create leaks, and washing can ruin its structure. Carbon filters can be aired out, but once saturated they generally need replacement for reliable odour control. Always follow your device manual.
How many replacement filters should you keep at home?
For most people, keeping one spare set is a smart move. It helps you replace on time, especially during smoke events or peak allergy season. If you are unsure which filter fits your unit, check your model name and the filter part number, then match it to the product description.
FAQs
How often should I replace my air purifier filter?
As a baseline, replace carbon filters every 3 to 6 months, HEPA filters every 6 to 12 months, and clean pre-filters every 2 to 4 weeks. If you have smoke, pets, high pollen, or renovations, you may need to replace sooner.
How do I know if my air purifier filter needs replacing?
Common signs include weaker airflow, more noise, odours returning quickly, a visibly clogged filter, or a filter indicator alert. If your HEPA blocks most light when held up to a bright window, it is usually close to end of life.
Can I wash a HEPA filter?
Most HEPA filters are not washable. Washing can damage the filter structure and reduce performance. Only wash a filter if your manufacturer specifically states it is washable.
Why does my carbon filter stop removing smells?
Activated carbon can become saturated. When that happens it may stop trapping odours even if the filter still looks clean. Homes with cooking odours, smoke, or strong VOC sources often need carbon changes more frequently.
Do air purifier filter lights reset automatically?
Many units require a manual reset after you change the filter. Check your manual or app, and reset the indicator so the timer matches your new filter.
Is it worth replacing filters or should I buy a new air purifier?
If the fan and electronics are working well, replacing filters is usually the best value because the filter is the part that does the cleaning. Consider replacing the unit only if it is failing, very noisy, or you need a bigger capacity for a larger room.
Next steps
- Shop air purifiers and replacement filters
- Therapy Air Ion filter set
- Air purifier NZ guide
- Best air purifier NZ
- Indoor air pollution: what it is and how to reduce it
- Best air purifier filter NZ: what to look for
- Air purifier filter cost NZ: what to budget for
- Air purifier filter vs HEPA filter: what is the difference?
- How to choose an air purifier filter
