Allens Industrial Products are the Australian distributor for SMH Products who are a leading manufacturer of specialist equipment to all industries and sectors where workers are at risk of contamination. From their manufacturing base in South Shields, SMH design and build specialist decontamination equipment that deal with asbestos removal and can also be adapted for a range of industries and different hazardous materials.
Negative Pressure Units are commonly called NPUs play a critical role in preventing the escape of airborne asbestos fibres from an enclosed asbestos removal work area. The Code of Practice on How to Safely Remove Asbestos has the below information.
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Airflow inside an enclosure is critical for the reduction of airborne asbestos. as noted in the code of practice consideration should be given to how to set up the enclosure, decontamination unit and negative pressure exhaust unit to enable optimum smooth flow of air through the enclosure so as to minimise dead air pockets. All Negative Pressure Units sold through Allens Industrial Products are airflow tested prior to sale to assist with the selection process.
A Dispersed Oil Particulate (DOP) test, as mentioned in the Australian Standard IEC 60335.2.69 Section AA.22.201.2, is a cost effective, definitive, factual test used around the world in many mature asbestos removal industries to test an appliance's efficiency. This is a critical step to ensure that there are no leaks in your H.E.P.A filter or in the seals inside your machine, ensuring the 99.995% efficiency requirement. All Negative Pressure Units sold through Allens Industrial Products are supplied with a valid DOP certificate.
An Air Scrubber or as sometimes called an Air Filtration Device, are commonly used in the mould remediation industry and are used to improve the quality of the air or on restoration projects where airborne contaminants are present or will be created/disturbed during the restoration process, such as mould, dust, fumes, etc.
With a Hepa filter efficiency of 99.97% these capture a wide range of compounds and prevents organism migration from location to location.
A Negative Pressure Unit is designed to create negative pressure inside an enclosure to prevent the escape of airborne particles. Air is drawn into the unit by a powerful motor and through a series of filters, with each filter operating with a higher efficiency than the last.
Typically, this will be a two-stage process: a pleated pre-filter which removes all larger particulates from the air, down to 10μm in diameter, and a secondary filter, typically a HEPA (High Efficiency Particulate Air) filter which captures smaller particulates. A HEPA filter captures at least 99.995% preventing the escape of airborne asbestos fibres from an enclosed asbestos removal work area. The NPU'S supplied with a current DOP certificate from time of purchase.
As mentioned above airflow plays a critical role for Negative Pressure Units so there are a number of different models available for all size jobs.
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SMH500 Negative Pressure Unit
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AMS 1500 Negative Pressure Unit
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| The NPU 500 is a portable, lightweight unit designed to provide a nominal airflow of 619 m³/hr. Ideal for small working areas. | The AMS 1500 produces an approximate airflow of 2200m³/hr nominal Ideal for small to medium size working areas. |
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SMH NPU2500 Negative Pressure Unit
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SMH5000 Negative Pressure Unit
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| The SMH2500 Negative Pressure unit powerful motor provides a huge nominal airflow of 2750m³/hr for what is still a relatively compact size and lightweight. Ideal for Medium to large size working areas. | SMH5000 Negative Pressure Unit powerful motors provide a huge nominal airflow of 5200m³/hr for what is still a relatively compact size and lightweight. Ideal for Large size working areas. |
| Model | Airflow (m³/hr) | Ideal Use Case | Weight | Material | DOP Tested | Notes |
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| SMH500 | 619 | Small enclosures | 19 kg | Lightweight design | Yes | Compact and portable; ideal for domestic and light commercial work. |
| AMS1500 | 2200 | Small to medium enclosures | 48 kg | Polypropylene | Yes | Durable mid-range unit. |
| SMH NPU2500 | 2750 | Medium to large enclosures | 46 kg | Moulded polyethylene | Yes | Weld-free body; compact and lightweight design. |
| SMH5000 | 5200 | Large-scale enclosures | 65 kg | Compact design | Yes | High airflow; ideal for large asbestos removal zones. |
We stock a full range of certified asbestos removal supplies to keep your job site safe and compliant.
Everything you need for safe and compliant asbestos removal — all in one place.
Ensure safety and compliance during asbestos removal projects with high-performance NPUs from Allens Industrial Products.
Compact and portable. Ideal for smaller enclosures or spot remediation tasks.
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Heavy-duty unit for medium-sized asbestos removal zones. Reliable airflow and durability.
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High-capacity NPU for major remediation projects and large enclosures.
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Got questions about choosing, using, or maintaining negative pressure units for asbestos removal? You're in the right place. Browse the answers below to learn more about fit, filters, usage best practices, and how to find the right gear for your workplace.
This will depend on the size of the enclosure and many other factors and is job specific. Please feel free to contact us with any requirements.
Yes and we recommend having the units serviced every 6 months to maintain efficiency. This includes a DOP Testing and Airflow Test.
DOP stands for Dispersed Oil Particulate. The test is performed to ensure that there are no leaks in your HEPA filter or in the seals inside your machine, ensuring the 99.995% efficiency requirement.
We stock a range of SMH units including models rated from 600 m³/hr to 5200 m³/hr to suit both small-scale and large-scale asbestos enclosures. Each unit is clearly labelled with its airflow output.
The SMH500 is lightweight, compact, and ideal for small enclosures or spot-removal jobs. It runs on a standard 240V power supply and features ergonomic handles for easy transport—making it perfect for domestic and light commercial work.
The SMH5000 delivers a powerful airflow of 5200 m³/hr, making it suitable for medium to large enclosures. It helps maintain proper negative pressure and is often used in large asbestos removal zones or commercial-scale worksites.
The seamless moulded plastic design reduces potential leak points and enhances durability. It also makes the unit easier to clean and decontaminate, which is essential when working in hazardous environments like asbestos removal zones.
We recommend the Omniguard Differential Pressure Monitor. Real-time monitoring with easy data transfer.
Yes! We carry SMH Products Negative Pressure Units in all our branches and can dispatch around Australia.
A NPU can be ordered online, or by contacting us via phone or email.
We offer nationwide delivery & collection service from our branches in Brisbane, Sydney and Melbourne. Your local branch will arrange this with you and let you know the costs.
Choosing the right Negative Pressure Unit is crucial for safe, compliant, and effective asbestos removal. At Allens Industrial Products, we supply industry-leading NPUs, air monitoring equipment, and full asbestos removal solutions — backed by over 40 years of Australian industry expertise.
Need help selecting the best model for your job? Contact our expert team for personalised advice, competitive pricing, and fast nationwide delivery.
Protect your workers, stay compliant, and keep your projects moving safely — trust Allens Industrial Products for all your asbestos removal needs.
Trusted by Australian industries for over 40 years, we deliver dependable Negative Pressure Units and Decontamination solutions with certified products, fast shipping, and expert support.
