Sensor could enhance safety of respiratory equipment

A new kind of sensor could warn emergency services personnel when carbon filters in their respirators have become dangerously saturated and are unsafe to use.

In a recent issue of the journal Advanced Materials, researchers from the University of California, San Diego, and Tyco Electronics described how they made the carbon nanostructures and demonstrated their potential use as microsensors for volatile organic compounds.

Emergency services personnel protect themselves from such vapours, whose composition is often unknown, by breathing through a gas mask. Airborne toxins stick to the carbon in the gas mask’s filter, trapping dangerous materials.

As the filters become saturated, chemicals will begin to pass through and there is no easy way to determine when the filter is spent. Current safety protocols base the timing of filter changes on how long the user has worn the mask.

‘The new sensors would provide a more accurate reading of how much material the carbon in the filters has actually absorbed,’ said team leader Michael Sailor, professor of chemistry and biochemistry and bioengineering at UC San Diego. ’Because these carbon nanofibres have the same chemical properties as the activated charcoal used in respirators, they have a similar ability to absorb organic pollutants.’

Sailor’s team assembled the nanofibres into repeating structures called photonic crystals that reflect specific wavelengths of light.

The iridescent sensors change colour when the fibres absorb toxins, giving a visible indication of their capacity for absorbing additional chemicals.

The materials that the team fabricated are very thin and Sailor’s group has previously placed similar photonic sensors on the tips of optical fibres less than a millimetre across and shown that they can be inserted into respirator cartridges.