Low Cost Wearable Multi-Gas Chemical Sensor Badges for First Responders

Abstract

IntroductionToxic Industrial Chemicals (TICs) are chemical substances which produce toxic effects if encountered in sufficient quantities and/or long durations. TICs are a great concern for the U.S. Department of Homeland Security (DHS) since they would be easier for terrorists to obtain and use than Chemical Warfare Agents (CWAs). Therefore, first responders need a small, rugged, wearable, monitor that alerts them when they are facing TICs, and if so, what is present and at what levels. While there are many commercially available handheld and personal gas monitors for TICs, most are bulky (more than 0.75” in thickness) and expensive ($500 or more). These monitors are primarily used in cities having a population of 100k or more. Hence, there is a need for a low cost (less than $100) wearable multi-gas sensor. Such wearable sensors will also find use in the much bigger application of industrial worker safety monitoring.To address this need TDA Research (TDA) has developed a simple, low cost wearable smart chemical sensor badge that has high sensitivity and selectivity to multiple TICs at trace (low parts per million) concentrations and triggers distinct alarms at permissible exposure limit (PEL), and Immediately Dangerous to Life or Health (IDLH) concentrations. Our wearable smart sensor badge uses a Lab-on-a-chip, is smaller than 2” x 2” x 0.75”, and can detect multiple TICs ( 4 to 6) of interest, and has a low rate of false alarms so that easy and widespread deployment can be achieved.TDA's sensorWe have demonstrated the operation of the sensor in a fully integrated prototype to detect four to six TICs among the H2S, NH3, PH3, HCN, Cl2, and NO2 at ppm levels and produce an electrical signal that can be used to identify and quantify them. We then obtained performance data that included results for these TICs both separately and together and in the presence of interferents, such as diesel and bleach. The sensor response was correlated and corrected based on ambient temperature, relative humidity levels and the air flow rate through the sensor. This low cost sensor is built using commercial-off-the-shelf (COTS) components along with TDA proprietary media and detection/quantification algorithms to detect and quantify TICs, eliminating false positives and false negatives. The sensors also have the ability to generate multiple alarms (audible, visual, and vibrate) at high (IDLH) and low (PEL) concentrations for four or more of the TICs in a small wearable form factor. TDA’s sensor has the unique ability to distinguish between different volatile organic compounds (VOCs) and oxidizes (Cl2, NO2 and even ozone). The attached figure is a photo of the TDA sensor. The results from the TDA sensor development and their performance under different threats at different humidity and temperature levels will be presented at the meeting. Figure 1