Wearable Chemical Sensor Badge

Abstract

Objectives Under this program, a wearable chemical detection badge capable of detecting and alarming (visual + audible/vibratory) in the presence of relevant concentrations of toxic industrial chemicals (TICs) in air has been developed and demonstrated for ammonia, chlorine, hydrogen sulfide, and nitrogen dioxide. The badge will alarm via one of the user-chosen alarm modes in the presence of ½ Immediately Dangerous to Life or Health (1/2 IDLH) concentrations of these TICs in under 5 minutes. The technology operates in harsh environmental conditions (10-90% RH, -10 – 50 oC) and in the presence of interferents (e.g. smoke, fuels, bleach and diesel exhaust). The active sampling badge consists of a reusable detection device that is used in conjunction with a disposable colorimetric sensor coupon. The sensor badge is unobtrusive and can be worn in the breathing zone of the user with hands-free operation for up to 8 hours on battery power. Results Small prototype devices (2” x 2” x 0.5”) were manufactured based on feedback from expert first responder personnel. Key points from this feedback include: Must have a low false alarm rate; no nuisance level alarms (e.g. PEL)Alarm must be very visible/noticeableMust be small and unobtrusiveData logging would be beneficial for analysis at a later time Prototype devices and associated sensor coupons were tested in the presence of PEL, ½ IDLH, and multiple IDLH concentrations of the target TIC analytes (ammonia, chlorine, hydrogen sulfide, and nitrogen dioxide) under harsh environmental conditions: -10 oC, ~ 90%RH 23 oC, 10% RH/50% RH/90% RH 50 oC, 10% RH/50% RH/90% RHand in the presence of environmental interferents including smoke (burning wood), diesel exhaust, diesel fuel and bleach. Utilizing four interrogation bands of the visible spectrum and combinatorial colorimetric response alarm criteria, the prototype badges performed well with no false positive or false negative alarms due to environmental interferent exposure, nuisance level (PEL) exposure, or harsh environmental conditions. Conclusion/Significance First Responders under duress need a simple, low-cost, rugged device capable of detecting the presence of harmful levels of Toxic Industrial Chemicals (TICs) with high fidelity while avoiding nuisance level alarms (e.g. OSHA PEL) and false alarms due to environmental contaminants (e.g. smoke, fuels, diesel exhaust). This prototype sensor technology fills an unmet need for the first responder and is adaptable for the incorporation of new sensors in the future. Figure 1