The Transit System Chemical Detection Challenge

The most significant challenge for the successful integration of advanced sensor technologies into a subway system is the need to sample, concentrate, and analyze the local atmospheric conditions in real time. Most available field-portable sensing technologies provide detection thresholds that are not ideal for the highly dynamic conditions in a transit system itself. Furthermore, due to atmospheric dilution of chemical and biological signatures, point detection systems are often inadequate without significant sampling and pre-concentration in the local environment. Typically, air circulators entrain large volumes of air, which is then filtered and sampled before being analyzed for the presence of contaminants. However, the air samplers and pre-concentrators developed to date are very bulky and power consuming for use in an economical and small system.

The air sampling or entrainment of chemical particles using the electrospray ionization (ESI) technology is based on research by Dr. John Fenn. The ESI sampler offers a unique and unprecedented combination of performance parameters including low power, lightweight and high sampling efficiency over an enormous range of particle sizes from molecules to microscale particulates. It is believed that a suitable sensor suite for chemical agents may include specialized molecularly imprinted polymers (MIPs) and/or surface acoustic wave devices (SAWs) combined with the aerosol collector. It is expected that this would be capable of detection needed for trace chemical species such Sarin, VX, other nerve agents, and various explosives.

Figure 1