What Is a Negative Pressure Unit and Do You Need One for Asbestos Removal?

July 2, 2026

Published by: DeconSafe Solutions | Category: Air Purifiers / Negative Pressure Units | Reading time: ~8 min

Introduction

If you are involved in asbestos removal in Australia, whether as a licensed contractor, a site manager, or a building owner overseeing remediation work, you have likely come across the term negative pressure unit. You may also have seen it referred to as an NPU, a negative air machine, or simply a negative air pressure unit.

Understanding what a negative pressure unit actually does, why it is required, and how it fits into the broader asbestos removal process is essential for anyone responsible for a safe and compliant worksite. Getting this wrong is not a minor oversight. It puts workers at risk of asbestos fibre exposure, exposes the surrounding environment to contamination, and can result in serious regulatory consequences under Australian WHS law.

This guide explains exactly what a negative pressure unit is, how it works, when it is legally required, and what to look for when selecting one for your project. At DeconSafe Solutions, as the sole authorised reseller of Deconta Group products in Australia and New Zealand, we supply NPUs for every type and scale of hazardous material removal project.

What Is a Negative Pressure Unit?

A negative pressure unit is a mechanical ventilation system designed to create a controlled low-pressure environment inside a sealed containment area. It achieves this by continuously extracting air from the contained work zone and exhausting it to the outside through high-efficiency filtration, typically HEPA filters rated at H13 or H14 grade.

Because the NPU removes more air from the space than enters it, the air pressure inside the containment zone drops below the surrounding area. This pressure difference means that air always flows inward through any gaps in the containment, rather than outward. Contaminated air containing asbestos fibres or other hazardous particles cannot escape the work zone into adjacent rooms, building systems, or occupied areas.

The extracted air does not simply vent to the atmosphere unfiltered. It passes through the NPU's filtration stages before being exhausted, ensuring that particles including asbestos fibres are captured before the air leaves the unit. Deconta NPUs, available exclusively through DeconSafe Solutions in Australia and New Zealand, use HEPA filtration that captures particles down to 0.3 microns at efficiency levels of 99.97% or greater, depending on filter grade.

How Does a Negative Pressure Unit Work in Practice?

On a typical asbestos removal site, the work zone is first sealed with polyethylene sheeting, barrier walls, and zipper doors to create a physical containment. The NPU is then positioned so that it draws air from inside this containment zone and exhausts it through flexible ducting to the outside of the building.

The unit runs continuously throughout the removal operation, maintaining the negative pressure differential at all times. If the containment barrier is breached or a door is opened without following the correct decontamination procedure, the airflow created by the NPU continues to direct any escaping air inward, limiting fibre release to clean areas.

Filter sensors on Deconta NPU models monitor the concentration of particles in the exhaust air continuously. If particle levels rise above set thresholds, the unit triggers both optical and acoustic alarms and displays a filter replacement alert, ensuring that filter condition does not silently degrade during operation. Some models also support IoT-enabled remote monitoring and control via smartphone, tablet, or computer, allowing supervisors to track airflow and pressure data in real time.

Is a Negative Pressure Unit Legally Required for Asbestos Removal in Australia?

Yes, in most licensed asbestos removal scenarios. Under Safe Work Australia's Code of Practice for the Safe Removal of Asbestos, and the Work Health and Safety (WHS) Regulations in all Australian states and territories, licensed asbestos removal must be conducted with appropriate controls to prevent asbestos fibre release beyond the work area.

Maintaining negative pressure inside the containment zone is one of the primary engineering controls required for Class A asbestos removal, which covers friable asbestos and any amount of friable asbestos-containing material. For Class B removal, which covers non-friable asbestos above 10 square metres, negative pressure requirements depend on the specific risk assessment and the conditions of the work environment.

In practice, the use of a negative pressure unit is the accepted method for demonstrating that the required containment controls are in place. Regulators and licensed asbestos assessors will expect to see a functioning NPU as part of any Class A removal setup.

What Is the Difference Between a Negative Pressure Unit and an Air Scrubber?

This is one of the most common points of confusion for contractors and site managers. Both NPUs and air scrubbers use HEPA filtration and look similar on the outside. Their purposes and the way they handle air are fundamentally different.

An air scrubber pulls air in, filters it through HEPA and sometimes activated carbon stages, and then recirculates that cleaned air back into the same space. The room air pressure does not change. This makes air scrubbers useful for improving air quality in spaces affected by dust, odour, mould, or smoke, but they do not contain or isolate hazardous particles within a sealed zone. Filtered air that stays in the room can still carry residual particles that escape through gaps.

A negative pressure unit, by contrast, physically exhausts filtered air outside the building. This creates the pressure differential that keeps contaminated air contained. It does not recirculate air within the work zone. For asbestos removal, the goal is not just to filter the air but to ensure that contaminated air cannot leave the containment zone. That is what an NPU is designed to achieve, and it is why NPUs are the required choice for licensed asbestos removal rather than air scrubbers.

For a detailed comparison of the two, see the DeconSafe blog post on Negative Pressure Unit vs Air Scrubber for Asbestos Removal.

What Types of Negative Pressure Units Does DeconSafe Solutions Supply?

DeconSafe Solutions stocks the complete Deconta range of negative pressure units, manufactured in Germany to the highest quality and safety standards. The key models available are as follows.

Deconta G55 Negative Pressure Unit is a compact, lightweight unit weighing 18.8 kg and measuring 525 x 390 x 390 mm. It is designed for smaller-scale hazardous material removal operations and confined spaces where a larger unit would not fit. Despite its size, the G55 delivers effective negative pressure control with HEPA filtration and is available with manual control or remote monitoring options. View the G55 product page for full specifications.

Deconta S200 Negative Pressure Unit delivers an airflow capacity of up to 4,200 m³/h and is designed for medium-sized operations requiring reliable and efficient air extraction. At 66 kg with dimensions of 845 x 718 x 790 mm, the S200 balances strong performance with practical portability. It is available with manual control (Control SE) or IoT-enabled remote monitoring (Control SRE connect). View the S200 product page.

Deconta S300 Negative Pressure Unit steps up performance further for large-scale industrial and commercial asbestos removal projects. The S300 is available for both purchase and hire, making it accessible for contractors who need high-capacity NPU performance for a single large project. View the S300 product page.

All Deconta NPUs are exclusively available through DeconSafe Solutions in Australia and New Zealand. Browse the full Negative Pressure Units collection.

How Does an NPU Work Alongside Other Site Equipment?

A negative pressure unit does not operate in isolation. It is one part of an integrated decontamination system that works together to keep the work zone contained and workers safe.

The NPU works alongside the physical containment to maintain negative pressure. It works with the decontamination shower positioned at the containment exit to ensure workers are decontaminated before leaving the hazardous zone. It works with water treatment systems that manage contaminated wastewater from the decontamination process. And it works with personal protective equipment worn by workers inside the containment zone.

On some sites, particularly those involving the SMART DOOR system, the NPU can be directly connected to the door's air supply flaps for automatic pressure-based door control, tightly integrating the entry and exit management of the containment zone with the NPU's operation.

For projects where air quality monitoring is required beyond the built-in filter sensors, the Deconta Negative Air Pressure Monitor provides precise, continuous monitoring with reporting and alarm features that support regulatory documentation requirements.

Common Mistakes Contractors Make with Negative Pressure Units

Running an undersized unit for the work zone. NPU sizing is based on the volume of the containment area. An underpowered unit cannot maintain adequate negative pressure in a large space, even if it is running at full capacity. This is one of the most common and most dangerous NPU errors on site.

Not maintaining the pressure differential throughout the job. The NPU must run continuously from the moment the containment is sealed until decontamination is complete. Switching it off during breaks or to reduce noise allows the pressure differential to equalise and contaminates the intended containment control.

Ignoring filter condition alerts. Deconta NPUs include filter monitoring systems that trigger alerts when filtration performance is degraded. Continuing to run a unit with a full or compromised filter reduces filtration efficiency and risks exhausting inadequately filtered air.

Using an air scrubber instead of an NPU for licensed removal work. This substitution is not compliant. An air scrubber does not create negative pressure and does not satisfy the containment requirements of the WHS Regulations for licensed asbestos removal.

Not accounting for duct length and routing. Exhaust ducting that is too long or poorly routed creates resistance that reduces effective airflow from the NPU. This should be assessed during site planning, not improvised on the day.

Frequently Asked Questions

Do I legally need a negative pressure unit for all asbestos removal work in Australia?

For Class A licensed asbestos removal, negative pressure containment is required under Australian WHS Regulations and the Safe Work Australia Code of Practice. For Class B removal, the requirement depends on the specific risk assessment and site conditions. If you are unsure what applies to your project, your licensed asbestos assessor can advise, or contact our team for guidance.

What is the difference between H13 and H14 HEPA filters in an NPU?

Both H13 and H14 are high-grade HEPA filter classifications under EN 1822. H13 filters capture at least 99.97% of particles at 0.3 microns. H14 filters capture at least 99.995% at the same particle size. For asbestos removal, H13 is commonly used, but H14 provides an additional margin of safety. Filter selection should align with your project's risk assessment and any specific requirements from your licensed asbestos assessor.

How do I know what size NPU to use for my containment zone?

NPU sizing is based on the volume of the containment area and the required number of air changes per hour. As a general guide, the NPU should be capable of achieving a minimum of four to ten air changes per hour in the containment zone, depending on the nature of the work. Our team at DeconSafe Solutions can help you select the right unit for your specific site. Get in touch here.

Can I hire a negative pressure unit in Australia?

Yes. DeconSafe Solutions offers NPUs for hire through our Hire Division, with flexible periods and nationwide coverage. This is a practical option for contractors who need NPU capacity for a single project without the upfront cost of purchasing.

Can I monitor my NPU remotely on site?

Yes. Deconta NPU models with the Control SRE connect option support IoT-enabled remote monitoring and control via PC, mobile, or tablet. This allows supervisors to track airflow, pressure data, and filter condition in real time without being physically present at the unit. See the S200 and S300 product pages for details.

Where can I buy a negative pressure unit in Australia?

DeconSafe Solutions is the sole authorised reseller of Deconta Group negative pressure units in Australia and New Zealand. Browse our full Negative Pressure Units collection or contact our team to discuss your requirements.

Final Thoughts

A negative pressure unit is not optional equipment for licensed asbestos removal in Australia. It is the primary engineering control that keeps contaminated air contained within the work zone and protects workers, bystanders, and the surrounding environment from asbestos fibre exposure.

Understanding how an NPU works, what distinguishes it from an air scrubber, and how it integrates with the rest of your decontamination setup puts you in a far stronger position when planning any asbestos removal project.

DeconSafe Solutions supplies the complete Deconta NPU range across Australia, with expert support for product selection, configuration, and deployment. Browse our Negative Pressure Units collection or contact our team to get started.

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