Air purifiers are one of the most heavily marketed products in the indoor air quality category, and mould is one of the most frequently cited conditions they are sold to address. The problem is that the air purifier market is full of products making claims that are not supported by the science, and some technologies actively worsen indoor air quality rather than improving it. This guide cuts through the marketing to explain which air purifier technologies genuinely reduce mould spore concentrations, which are ineffective, and what role a purifier can realistically play in an Illawarra home with mould challenges. See our indoor air quality testing guide if you want to measure the problem before purchasing a solution.
Quick Answer (BLUF)
True HEPA air purifiers effectively capture mould spores from the air and are a genuinely useful tool for reducing airborne spore concentrations, particularly for allergy or asthma sufferers. They do not kill mould at its source, stop mould growing, or reduce humidity. Ionic purifiers, ozone generators, and photocatalytic (PCO) units are either ineffective for mould or can produce harmful byproducts. Never use an ozone generator in an occupied space.
What an Air Purifier Can and Cannot Do
Can do:
- Remove airborne mould spores from the room air (HEPA filtration)
- Reduce the concentration of airborne allergens (spores, mycotoxin particles) that occupants inhale
- Provide benefit for people with mould allergies, asthma, or respiratory conditions while mould remediation is underway or while waiting for professional treatment
- Supplement (not replace) a remediation and moisture control strategy
Cannot do:
- Stop mould growing on surfaces, that requires removing the moisture source and treating existing colonies
- Reduce indoor relative humidity, that requires a dehumidifier
- Clean the air in rooms it is not running in
- Fix a mould problem, it manages symptoms of elevated spore counts, not the cause
Technology Guide: What Works
True HEPA Filtration, Recommended
HEPA (High Efficiency Particulate Air) filters capture 99.97% of particles 0.3 microns and larger. Mould spores range from approximately 1-100 microns, well within the capture range of a true HEPA filter.
For mould management in an Illawarra home, a true HEPA purifier:
- Reduces the airborne spore count in the room it operates in continuously
- Provides measurable symptom relief for mould-sensitive occupants
- Is most effective in a bedroom (where occupants spend 6-8 hours) or living area
What to look for:
- “True HEPA” or “H13 HEPA” certification, not “HEPA-type” or “HEPA-like” (these are marketing terms with no standard performance requirement)
- CADR (Clean Air Delivery Rate) appropriate to the room size, as a rough guide, CADR in m³/h should be approximately 3-5 times the room volume in m³ for effective air changes
- A pre-filter for larger particles (extending HEPA filter life) and ideally an activated carbon stage for volatile organic compounds (mould off-gassing)
Limitations: A HEPA purifier captures spores that are airborne, not spores sitting on surfaces or growing in wall cavities. In a heavily mould-contaminated home, the spore source is much larger than a purifier can manage.
Activated Carbon, Useful Addition
Activated carbon filters adsorb gases and volatile organic compounds, including the VOCs (MVOCs) that give mouldy spaces their musty smell. Carbon does not capture particulate matter (spores), but a combined HEPA + carbon unit addresses both particles and gases from mould growth. Useful for occupants who are bothered by the smell as well as health effects.
Technology Guide: What Doesn’t Work or Is Harmful
Ozone Generators, Do Not Use in Occupied Spaces
Ozone generators are sometimes marketed as mould killers because ozone (O₃) can oxidise biological material including mould. The problem: the ozone concentrations required to kill mould on surfaces are far higher than safe limits for human inhalation. Ozone at those levels damages lungs, irritates airways, and can trigger asthma attacks. The US EPA explicitly warns against the use of ozone generators in occupied spaces.
Ozone generators have a legitimate professional use, specifically, high-concentration shock treatment of unoccupied spaces, but they are not appropriate for household use as an ongoing air quality management tool.
Ionic/Electrostatic Purifiers, Limited Effectiveness
Ionic purifiers charge airborne particles so they adhere to surfaces (walls, floors, furniture). This removes particles from the air but deposits them on surfaces, where they can be disturbed and re-aerosolised by normal movement. They do not capture and contain particles the way a HEPA filter does. Some ionic units also produce small quantities of ozone as a byproduct.
UV-C Germicidal Lamps, Limited Real-World Effectiveness
UV-C light can kill mould spores in direct, sustained exposure. In an air purifier, spores pass the UV-C lamp for a fraction of a second, not long enough for effective kill at the intensities used in consumer products. UV-C is most effective in duct systems with longer exposure time, or in HVAC applications. Consumer air purifier UV-C stages add cost without meaningful mould management benefit.
Photocatalytic Oxidation (PCO), Not Recommended
PCO technology uses UV light to activate a titanium dioxide catalyst, producing hydroxyl radicals and other reactive oxygen species that theoretically break down VOCs and biological contaminants. In practice, consumer PCO units produce ozone and potentially harmful aldehyde byproducts (including formaldehyde) as reaction products. The California Air Resources Board has found many PCO products to emit ozone at levels that can worsen air quality.
Selecting a HEPA Purifier for an Illawarra Home
The Illawarra’s coastal humidity means that air purifiers in this region work harder and should be chosen with this in mind:
- A high-ambient-humidity environment means filters load faster with dust, pollen, and organic material, choose a unit with an accessible, easy-to-replace HEPA filter
- Salt and fine marine aerosol on the coast (from Thirroul to Port Kembla) is corrosive, look for units with better-sealed construction
- For bedrooms, noise level matters, look for units rated below 30 dB on their lowest setting
- Running costs: a quality HEPA unit draws 20-60W continuously, this is modest, but filter replacement (typically $50 to $150 per year) is an ongoing cost
FAQs
Can an air purifier replace professional mould remediation?
No. A HEPA purifier reduces airborne spore concentrations in the room it operates in but does not address mould growing on surfaces or in building materials. It is a symptom management tool, not a remediation tool. Use it alongside, not instead of, professional mould remediation.
Should I run an air purifier during mould remediation?
Not in the work zone, the remediation activity will overwhelm any consumer purifier’s capacity, and the unit itself may become contaminated. A commercial-grade HEPA air scrubber (different from a consumer purifier) is used by professionals as part of the containment system during active remediation. In other rooms of the house outside the work zone, a HEPA purifier can help maintain air quality.
How do I know if an air purifier is making a difference?
A professional air quality test before and after running a purifier for several weeks can quantify the improvement in spore counts. Consumer air quality monitors provide some indication of particle concentrations (PM2.5, PM10) but are not calibrated for mould spore identification.
Do air purifiers help with the mould smell?
A unit with an activated carbon stage will reduce the musty VOC smell associated with mould growth. However, if the mould source itself is not addressed, the VOC production is continuous and the carbon filter will saturate relatively quickly, requiring replacement.