Also known as “The Truth About HEPA Filters – What NZ Restoration Professionals Need to Know,” this guide breaks down real HEPA standards, system tips, and training insights…
HEPA filters get mentioned a lot in the cleaning, remediation, and restoration space – but do you know what makes a filter actually HEPA? If you’re a professional working with mould, asbestos, water damage, or fire restoration in New Zealand, chances are you’re using air scrubbers, negative air machines, or vacuums with HEPA filters in the mix. But not all HEPA claims are created equal.
Let’s cut through the marketing fluff and break down what “true HEPA” really means – and why it matters for your jobs, your clients, and compliance in the NZ industry. This guide also supports CSL’s IICRC training pathways – including WRT, AMRT, FSRT, OCT, and HST – so you can confidently apply what you learn in the field.
What Does “HEPA” Really Mean?
The term “HEPA” stands for High Efficiency Particulate Air, and to be classed as true HEPA, a filter must:
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Capture 99.97% of particles at 0.3 microns (according to U.S. DOE standards).
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Meet ISO 29463 or EN 1822 classifications, typically H13 or H14, which are accepted in New Zealand.
Watch out for filters labelled as “HEPA-type” or “HEPA-style” – these often fall well short of true HEPA performance. A 99% filter allows 30 times more particles through than true HEPA, and a 95% filter leaks 165 times more.
That’s a big risk on a mould, flood, or trauma cleanup job. In regulated environments like AMRT or FSRT restoration, substandard filtration could mean failed clearances—or worse, unsafe exposure for your team or clients.
How Do HEPA Filters Work?
True HEPA filters don’t work like sieves. Instead, they trap particles through three separate mechanisms:
| Mechanism | Particle Size | How It Works |
|---|---|---|
| Diffusion | <0.1 μm | Particles zigzag (Brownian motion) and collide with fibres |
| Interception | ~0.3 μm | Particles follow airflow and stick when brushing past fibres |
| Impaction | >0.4 μm | Large particles can’t change direction fast enough and hit fibres directly |
This multi-method capture makes HEPA filters uniquely effective at removing a wide range of contaminants, including dust, mould spores, bacteria, and viruses. It’s also why these principles are covered in detail in OCT, AMRT, and WRT training.
Go Beyond HEPA: CSL Smart Vacs with S-Class Filtration
While HEPA is the gold standard in many restoration scenarios, CSL offers Smart Vac units with S-Class (hospital-grade) filtration, which exceeds HEPA performance. These vacuums: 
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Filter down to 0.3 μm with 99.99% efficiency, independently tested.
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Are certified to EN 1822 H13/H14 AND meet S-Class filtration standards.
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Offer additional protection against viruses, bacteria, fine dust, mould spores, and even fentanyl residue.
Smart Vacs are a popular choice among NZ restoration professionals handling AMRT, HST, or trauma scene cleanups. They’re powerful, portable, and offer unmatched filtration confidence—essential when health risks are high and contamination is invisible.
???? Explore Smart Vacs on our website →
What to Look for in a True HEPA System
It’s not just about the filter media—the whole system needs to perform. Make sure your equipment ticks these boxes:
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Individually tested and certified filters (not just media claims).
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Tested at operating airflow rates—not idealised lab settings.
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Leak-proof housing and gaskets to prevent bypass.
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Pre-filters and carbon stages to protect and extend HEPA life.
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Quality media, preferably micro-glass, not synthetic.
These are all topics covered across WRT, HST, and OCT courses, ensuring you’re equipped to assess your own tools—and your team’s safety.
Understanding HEPA Units in NZ Restoration
You’ll typically encounter three styles of HEPA-equipped systems: 
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Negative Air Machines (NAMs)
Ideal for containment zones. Big airflow, rugged casing, not always portable. -
Compact Air Scrubbers
Flexible and mobile. Good for sealed rooms or multi-level jobs. -
HEPA Vacuum Systems (e.g. Smart Vacs)
For detailed surface cleaning, decontamination, and final clearance stages.
To ensure effective air changes, choose a unit with a CADR (Clean Air Delivery Rate) that meets or exceeds 4–6 room air changes per hour.
Filter Maintenance: Clean Air, Clean Reputation
Even the best HEPA filter loses effectiveness over time. Watch for:
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Reduced airflow or CFM drop.
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Persistent odours after carbon filtration.
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6-month usage in standard environments – or sooner with heavy particulate loads.
Never clean a HEPA filter by banging or vacuuming unless explicitly designed to be washed. You could destroy the integrity of the fibres or release trapped particles.
In FSRT, WRT, and AMRT environments, a clogged or damaged filter can halt your drying plan – or your compliance.
What About DIY Filters?
Corsi-Rosenthal boxes (box fan + MERV filters) gained popularity during the pandemic for home use. While they’re effective in casual settings, they aren’t suitable – or compliant – for professional remediation or restoration work in NZ.
Stick with certified HEPA or S-Class systems if you want protection you can trust—and results that pass verification.
Final Word: Train Smart, Filter Smarter
HEPA and S-Class filtration is at the heart of safe, professional remediation in New Zealand. Whether you’re drying flood-affected structures, removing mould, or handling smoke-impacted environments, understanding your filtration tools is essential.
✅ Use true HEPA or hospital-grade S-Class filtration
✅ Keep your systems tested, sealed, and well-maintained
✅ Invest in the training that backs up your practice – WRT, AMRT, FSRT, OCT, HST
(click images for course details)
