When asbestos is disturbed, microscopic fibres can become airborne and pose serious health risks — which is why licensed asbestos removal specialists follow strict containment procedures before a single piece of material is touched. In New Zealand, these procedures are governed by the Health and Safety at Work (Asbestos) Regulations 2016 and overseen by WorkSafe NZ. Understanding what good containment looks like helps you know what to expect when you hire a specialist.
Why Containment Matters
Asbestos fibres are invisible to the naked eye. Once airborne, they can travel through a building via air currents, ventilation systems, and foot traffic — contaminating areas far beyond the original work zone. Proper containment keeps fibres localised, protects the occupants of the building, neighbouring properties, and the workers themselves.
Class A vs Class B Removal
NZ regulations distinguish between two classes of licensed asbestos removal work:
- Class B removal covers non-friable asbestos (bonded material, such as fibro cement sheeting like James Hardie products) that is in good condition and being removed with minimal disturbance.
- Class A removal covers friable asbestos (loose, crumbly material) or any non-friable material that will be significantly disturbed. Class A work requires the most rigorous containment.
The class of licence held by the contractor determines what work they can legally perform. Always confirm your specialist holds the appropriate licence for your job.
Setting Up the Containment Enclosure
For Class A removals — and many Class B jobs — specialists construct a full containment enclosure around the work area. Here's how it typically works:
1. Isolating the Zone
- All people not involved in the removal are excluded from the area.
- HVAC systems, fans, and ventilation ducts serving the zone are switched off and sealed to prevent fibre migration.
- Doorways, windows, and gaps are sealed with heavy-duty polyethylene sheeting (typically at least 200 µm thick), secured with duct tape.
2. Building the Enclosure
- A double or triple layer of poly sheeting is draped over walls, floors, and ceilings within the work zone, creating a sealed "room within a room."
- Floors are given particular attention — sheeting is lapped up the walls and taped to create a continuous barrier.
- For outdoor work, temporary enclosures or tenting structures may be erected and weighted or tied down to prevent wind disturbance.
3. Negative Air Pressure Units (NAPs)
- One of the most critical elements of Class A containment is the use of negative air pressure units fitted with HEPA filters (High Efficiency Particulate Air).
- These machines continuously draw air out of the enclosure, exhausting it through the HEPA filter to the outside. This means air flows into the enclosure from the surrounding building — not out — so fibres cannot escape.
- The number and capacity of NAP units is calculated based on the volume of the enclosure.
4. Decontamination Units
- A decontamination unit (DCU) — essentially a series of airlocks — is attached to the enclosure entry point.
- Workers pass through a dirty change room, a shower/wash area, and a clean change room when entering and exiting.
- This prevents fibres from being carried out on clothing, skin, or equipment.
Personal Protective Equipment (PPE)
Inside the enclosure, workers wear:
| PPE Item | Purpose |
|---|---|
| Full-face or half-face respirator with P3 filter | Prevents inhalation of fibres |
| Disposable coveralls (Tyvek-style) | Stops fibres settling on clothing |
| Gloves and boot covers | Prevents skin contact and tracking |
| Eye protection (if not full-face) | Protects eyes from dust |
All disposable PPE is treated as asbestos-contaminated waste and bagged inside the enclosure before workers exit through the DCU.
Wet Methods and Fibre Suppression
Specialists use wet methods wherever practicable — misting or spraying asbestos-containing materials with water or an amended water solution before and during removal. Keeping the material damp dramatically reduces the number of fibres released into the air.
Air Monitoring
For Class A removals, independent air monitoring is required. A licensed asbestos assessor (a separate role from the removalist) takes air samples inside and outside the enclosure during and after removal. Results must confirm fibre levels are below the clearance standard before the enclosure is dismantled and the area is handed back. BRANZ provides useful technical guidance on testing and assessment practices.
Waste Disposal
All removed asbestos material, contaminated sheeting, PPE, and cleaning materials are double-bagged in heavy-duty, labelled poly bags and disposed of at a licensed facility. Asbestos waste cannot go into general skip bins or household rubbish. Your specialist should provide documentation of lawful disposal.
When to Call a Professional
Asbestos removal is restricted work in New Zealand. Under the Health and Safety at Work (Asbestos) Regulations 2016, any removal of more than 10 m² of non-friable asbestos, or any amount of friable asbestos, must be carried out by a licensed asbestos removalist. Homeowners must not attempt this work themselves. Even small disturbances of suspect material can be hazardous — if you're unsure whether a material contains asbestos, have it tested by a licensed asbestos assessor before doing anything.
For guidance on your obligations as a property owner or PCBU, visit WorkSafe NZ and MBIE Building Performance. You can find qualified, licensed asbestos removal specialists in your area on tradedirectory.co.nz.
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