How our detector works

How Asbestos is Currently Detected

Currently, the most common way to identify hazardous airborne asbestos at worksites is to filter the air, count the number of fibres that are caught, and later analyse the fibres with X-ray technology to determine if they are asbestos.

This approach requires expensive lab work and hours of wait time.

An alternative method to evaluate work site safety is to use a real-time fibre detector, but the current, commercially available detectors are unable to distinguish between asbestos and other less dangerous fibers such as mineral wool, gypsum and glass.

Lab Testing Asbestos

Alert's Method 

The University of Hertfordshire, specialists in the field of particle detection and Alert's partners in the FP7 funded R&D project, developed a new warning method, which in contrast can identify asbestos on-site. It does so by employing a laser-based technique that takes advantage of the magnetic properties of the mineral.

The Asbestos ALERT works by measuring both the laser light scattering and magnetic properties of individual respirable particles in the air at rates of hundreds of particles per second. From the light scattering it determines whether or not the particle is a respirable fibre, and then assesses how that fibre behaves in a strong magnetic field. Asbestos fibres are paramagnetic*, meaning they are not normally magnetic but become so in a magnetic field and can therefore be rotated by that field.

“We can use this technique of light scattering to anaylse single airborne fibres that are far too small to be seen with the naked eye,”he says. After identifying the fibres, the device carries them in an airflow through a magnetic field, and uses light scattering again on the other side to tell if the fibres have aligned with the field.  “If they have, they are highly likely to be asbestos,” Kaye says.

ALERT records this behaviour and uses it to make an assessment of the probability of asbestos being present, to a confidence level of 99%. It then warns the user of the risk of inadvertent exposure to airborne asbestos, allowing them to take immediate action to leave the vicinity or don a suitable protective breathing mask.

When exposed to a magnetic field, asbestos fibres orient themselves to align with the field. The property is virtually unique* among fibrous materials. “Asbestos has a complex crystalline structure containing several metals including silicon, magnesium and iron. It is thought that it is the iron atoms that give rise to the magnetic properties, but the exact mechanism is still somewhat unclear,” says Kaye.

The Hertfordshire team’s new warning method, developed under the European Commission FP7 project ‘ALERT’ (FP7-SME-2008-2), works by:

  1. First shining a laser beam at a stream of airborne particles.
  2. When light bounces off the particles, it scatters to form unique, complex patterns

The light scattering pattern created by the fibres “is a bit like a thumbprint for the particle,” says Kaye, sometimes making it possible to identify a particle’s shape, size, structure, and orientation by looking at the scattered light.

*Certain types of man-made fibre such as steel or magnetically engineered fibres may have similar magnetic properties to those of asbestos and could therefore be wrongly assessed as asbestos. However, unlike asbestos, such fibres are never normally found in the ambient airborne environment where building, renovation, or demolition work is being undertaken. 


The team has tested the Asbestos ALERT in the lab and has worked with colleagues in the U.K. and Spain to develop prototypes that have undergone field trials at various locations where asbestos removal operations were underway.

Kaye notes that his team wasn’t the first to try to exploit the magnetic effect to develop an asbestos detector.

Laser scan


Alert Technology Ltd, a spin off The Select Group of Companies (the ALERT FP7 project's Exploitation Managers) are responsible for production and commercialization of the Asbestos ALERT.

A limited number of pre-production sample units are being developed in readiness for robust field trials in a variety of industry sectors. For updates on future launch dates please sign up for our newsletter or contact Alert 

Prices for the Asbestos ALERT range have not yet been fixed but there are plans to launch the Asbestos ALERT Pro model first aimed at professionals who require downloadable information.

The price of the future smaller 'Tradesman's Model' has not yet been released but it is Alert Technology's aim to make the device affordable in line with other electronic instruments used regularly by the trade, with the hope that as production increases after the initial product launch, that costs may be reduced further making the detectors even more affordable for an individual plumber, electrician or building renovator.  

“These tradespeople are the most frequently affected by asbestos-related diseases and most who get the diseases will die from them,” the team says. 

The company have also identified a number of industry specific models for future development alon with a Fixed Perimeter Model that works to clearance levels.

Alert Asbestos Detector Concepts

ALERT Technology hope, over time, the new Asbestos ALERT Device will help to reduce the 100,000 annual death toll that the World Health Organization attributes to occupational exposure to airborne asbestos.


British Lung Foundation


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