Bio Aerosol Fluorescence

The IBAC 2 is a real-time optical sensor that counts individual airborne particulates and provides the ability to discriminate a biological agent based on elastic scattering and fluorescence emission. The sensor operates by pulling air particles into the device at four liters/minute. The particles pass through an optical illumination region where they are excited by a continuous-wave laser beam. The light pulses that scatter off the particles are measured to determine size and concentration. Simultaneously, the wavelength of the light emitted from the particles is measured to determine fluorescence. If the emitted light falls within a specific wavelength band, the particles are fluorescent and considered a biological particle.

The sensor has been independently tested by US government and military to reliably detect all four classes of biological agents – spores, vegetative, virus, and toxins - in less than 60 seconds at concentrations below 100 ACPLA. The IBAC 2 has received DHS Safety Act Designation.

The IBAC 2 is designed to monitor the air continuously with a sample illumination and signal processing approach that permits single-particle optical interrogation at high aerosol concentrations (500,000 particles/liter) with low particle coincidence. The particle detection region is a simple and rugged design shown to stay clean for many months in the dirtiest of environments, offering a high maintenance interval and simple procedure for optics cleaning. The laser diode offers a highly reliable excitation source with a lifetime approaching 50,000 hours. Photomultiplier tubes are used for elastic scatter and fluorescence detection offering a temperature tolerant optical receiver approach and the sensor has an internal compensation method for photomultiplier degradation. The air intake stack and the sensor’s enclosure have been designed to allow the sensor to operate in all types of weather conditions such as rain, sleet, snow, or high winds.

In addition to providing real-time alerts to biological aerosol threats, the IBAC 2 can trigger a secondary aerosol sample for subsequent analysis and identification. The integrated collector consists of a high flow air sampling pump that collects a physical sample of aerosol particles using two options: dry collection or wet collection. For dry collection, air is drawn through a 47-mm DFU polyester filter (PEF-1). The filter can be transferred into a sample vial and processed in a manner that yields a liquid suspension.



Figure 1. Fluorescence emission wavelength band

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The IBAC 2 is a fully automated biological agent detector that provides 24/7 monitoring. It alarms in less than 60 seconds when an airborne bio-threat is present, which triggers an onboard or remote sampler to collect a real-time sample for eventual analysis.

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