Sensing for safety

New sensing technologies are required to ensure health and safety in our homes, workplaces and on transport systems, says Dr Simon Aliwell

At 9.39am on 22 October, a Thomson flight carrying 154 holidaymakers and seven crew was forced to make an emergency landing at Stansted airport. The flight from Newcastle was bound for Larnaca in Cyprus but had to be diverted after a mid-air emergency caused by smoke and haze in the cabin and cockpit. The captain raised the alarm, the control tower mobilised emergency crews, and flight TOM2807 landed safely.

But the incident, which raises concerns about air safety, was no anomaly. Five almost identical incidents were reported in the same week (two on the same day), suggesting a greater threat to passenger and crew safety than we currently perceive. Of most concern is the fact the cockpit crew of TOM2807 was only alerted to a problem when they saw contaminated air in the form of smoke.

Air comes into the cockpit of an aircraft via the engines. It is usually clean, though fuel or hydraulic fluid leaks can occasionally cause contamination. This cannot always be seen until it is too late to control and it frequently can’t be seen at all. But it is always a potential risk to crew and passenger safety. This prompts a very important question - why aren’t aircraft fitted with chemical sensors to identify threats before they occur?

Air quality is just one of many factors we must monitor to ensure health and safety in the workplace, our homes and on transport systems. We rely on our bodies to alert us if something is wrong. We assume the air around us is clean and free of toxins unless we sense otherwise.

But our biological systems are not sensitive enough to detect some of the most harmful substances, especially when we are asleep. Unless we are already aware how a dangerous substance looks, smells, feels or tastes, and are actively seeking it, we might not identify a threat. Even then, detection could come too late.

Carbon monoxide is lethal, but has no smell and no taste to humans. It can’t be seen. The recent tragic death of two British children in Greece from carbon monoxide poisoning is a sobering example of how important it is to identify the presence of dangerous substances before they present a risk.  We need technology to step in and support human detection.

Sensing is a big global business. The global sensor market is estimated to reach in excess of £25bn by 2008. It encompasses everything from water pollution monitoring to disease detection and measuring the state of foundations in buildings. Health and safety is one of the largest sensing markets.

Sensors can be used in almost any circumstance where personal safety is at risk. New research into micro and nanotechnology is starting to uncover fresh ways to detect chemicals and identify the presence of dangerous substances by recognising just a single particle. Over the next few years we can expect to see a raft of new sensing technologies entering the health and safety market.

First we have to tackle some substantial challenges. Conventional detection technologies, such as Ion Mobility Spectrometers (IMS), are built for non-domestic use by specialists in industry or the military. They are large, expensive to produce and have performance limitations such as frequent false-positives. This is unacceptable when dealing with personal safety.

New devices are required to meet emerging requirements for health and safety sensing in domestic or civil environments such as train stations, homes or offices. It would be impractical to simply deploy industrial-scale screening devices of the type found at airports and factories. Their size and cost, and the problems of evacuation due to false alarms, make them impractical.

Fundamental limits to the miniaturisation of these instruments also make them unsuitable for portable applications such as hand-held screening of trucks as they pass through ferry ports. New sensing technologies need to be deployed in devices which are small, light, simple to use, and energy efficient.

Companies like Owlstone Nanotech in Cambridge are already demonstrating the next generation of sensing technology. It is using nanotechnology to create selective chemical sensors smaller than a 50p coin. Owlstone’s system is quicker and easier to use than current detection methods, and it requires very little power.

At the heart of its technology is a breakthrough silicon sensor that can be reprogrammed to detect a wide range of airborne or dissolved chemical agents in extremely small quantities. It works by using a proprietary form of Field Asymmetric Ion Mobility Spectrometry (FAIMS), a sensitive and proven method of trace detection. FAIMS is a variant of Ion Mobility Spectrometry (IMS), the current method of choice for the detection of chemical warfare agents and explosives in the field.

The basic problem is how to detect the chemical of interest in a complex mixture. Owlstone’s technology identifies chemicals using a property know as mobility, a measure of how quickly an ion moves through an electric field. Mobility relates to size and mass, and is used to specifically distinguish and identify the chemical of interest. A chemical fingerprint is generated for each substance based on its mobility. The system can search for multiple substances at once or detect the presence of a single particle of a specified chemical.

Owlstone has just won a contract to develop its sensors for detecting fuel and chemical leaks in military aircraft cockpits. If successful, these devices could find their way into civilian aircraft or even trains, buses and cars.

By Dr Simon Aliwell
Dr Aliwell is director of the Sensors Knowledge Transfer Network, which is managed on behalf of DTI by the National Physical Laboratory and Qi3.