" (NATIBO, 2001) The method of operation of a "bubbler or impinger" is through "drawing aerosols through a current inlet tube and jet. Usually the jet is submerged in the liquid contained in the sampler." (NATIBO, 2001) the aerosol particles become capture din the base of the jet by the surface of the liquid as the air moves through the liquid. Collection of the smallest of the particles is enabled by a "small critical orifice causing the flow to become sonic." (NATIBO, 2001)There are designs that also form bubbles in the liquid as air leaves the jet which is fitted. The Variable Particle-Size Impactors are stated to generally have."..multiple stages" in which "each stage contains a number of precision-drilled orifices that are appropriate for the size of the participle to be collected in that stage and orifice sizes decrease with each succeeding impactor state." (NATIBO, 2001) as particles in the air are collected in the instrument, they are forced toward the surface collector by the orifices of the jet. Particles uncollected at that stage follow the air stream around the collection surfaces edge to the next stage.

Two Types of Triggers in Bio-Sensing Technologies

Technologies used in detection and triggering include: (1) a simple trigger; and (2) a complex trigger. The simple trigger is stated to "...respond to an increase in the atmospheric particulate background count or concentration. Once the threshold is breached, it activates the more complex and precise detector element to determine the nature of the suspected agent." (NATIBO, 2001)

Flow Cytometry

Cytometry is stated to refer "to the measurement of both the physical and chemical characteristics of cells. Flow cytometry refers to this same technique in which the characteristic measurements are made as the cells or other participles, which are present in a moving fluid stream, pass through an interrogation point." (NATIBO, 2001) This technology is a "hybrid technology" in which development in computer processing, optoelectronics, monoclonal antibody production, flurochrome chemistry and laser technology are all combined to make provision of a method that is automated in making analysis of bio-chemical properties. (NATIBO, 2001; paraphrased) This technique is one which "permits characterization and identification of biochemical species within a heterogeneous mixture of organic and inorganic material." (NATIBO, 2001) Flow Cytometry enables the measurement of the "physical and chemical characteristics of cells or particles." The following table shows the structural characteristic so biological cells measurable by flow cytometry.

Structural Characteristics of Biological Cells Measurable by Flow Cytometry

Source: (NATIBO, 2001)

Stated as advantages of using flow cytometry for biological sensing are the advantages as follows:

1) Fast sample preparation and analysis;

2) Single particle analysis;

3) Detection and identification in one instrument;

4) Significant multiplexing advantages;

5) Easily quantifiable results;

6) Adaptability to high, automated throughput;

7) Simple to operate; and 8) Compact instrumentation. (NATIBO, 2001)

Mass Spectrometry (MS)

Mass spectrometers separate ionized atoms and molecules from each other through using the mass-to-charge ratio differential. Mass Spectrometry is useful for "quantification of atoms or molecules and also for determining chemical and structural information about molecules." (NATIBO, 2001) Mass spectroscopy is a process that re-assembles fragments and then works in a fashion of backing up to bring about a generation of the original molecule. Stated to be the general operation of a mass spectrometer is the creation of "gas-phase ions" and then separation of the ions in space or in time "based upon their mass-to-charge ratio. The process known as resolution is one in which the mass spectrometers power is used in a process of separating ions dependent on their mass-to-charge ratio. Resolutions is defined as follows:

m/m where m is the ion mass and m is the difference in mass between two resolvable peaks in a mass spectrum." (NATIBO, 2001)

The ionization techniques used by mass spectrometers are varied with the various techniques producing different degrees of "fragmentation and organic compounds and therefore producing varying results for analysis." (NATIBO, 2001) Some of the various mass spectrometry techniques include the following:

1) Electron Impact Ionization;

2) Chemical Ionization;

3) Fast Atom Bombardment (FAB);

4) Electrospray Ionization (ESI); and 5) in MALDI in which the analyte is diluted in a solid or liquid matrix which strongly absorbs laser light. (NATIBO, 2001)

The analyzer that mass spectrometers use to quantify the ions by their mass-to-charge ratios are calibrated and there are several types of these analyzers which include the following:

1) Fourier-transform mass spectrometers;

2) Ion-trap mass spectrometers;

3) Time-of-Flight mass spectrometer; and 4) Quadrupole mass filter consisting of four rods. (NATIBO, 2001)

Hand Held Immunochromatographic Assays (HHA)

The Hand Held Immunochromatrographic Assays (HHA)...

Presently the HHA has the capacity to make identification of eight biological warfare threats and four stimulant agents. (NATIBO, 2001) the HHA is very simple to use and instructions state as follows: "...a small quantity of solution containing the suspected agent is placed in a well on the assay. Over a 15-minute period, the solution wicks through the assay where it is successively exposed to different antibodies. The first antibodies flow up the assay as soon as they come in contact with the solution and bind themselves to the specific biological warfare agent, if it is present. A second region of antibodies is moored to the assay's test area, where they immobilize the biological warfare agent (along with the bound antibodies). An enzyme attached to the moored antibody changes the color of a coating on the assay when this antibody binds to the biological warfare agent. A change in the color of this region is evidence of a positive test." (NATIBO, 2001) Presently the Department of Defense is concentrating on development of: (1) Hand-held bio-sensors that detect airborne biological agents with clear signal, affordable and with a low false alarm rate; (2) Ion-detection devices that can continuously monitor the air for BW agents; and (3) Non-intrusive detection of biological agents. (NATIBO, 2001) it is related that there is ongoing development of "several stand-alone detectors." NATIBO, 2001)
The goals set out in this development is the reduction of the "dependence on reagents and size, weight and power requirements of existing systems." (NATIBO, 2001) These technological challenges are presently being addressed in DoD research. Stated as a 'key hurdle' to effective coordination of joint detection systems "is determining how to be collaborate between civilian and military CB detection measures." (NATIBO, 2001) the stated goal of DARPA's Sensor Integration and Modeling for Biological Agent Detection (SIMBAD) program is the development and demonstration of sensor system prototypes for CB agent detection which are "fully integrated and well-characterized." (NATIBO, 2001) SIMBAD is stated to be inclusive of, although not limited to the technologies as follows:

Time-of-flight spectrometers;

Antibody-based sensors;

PCR-based sensor for DNA analysis;

Hyperspectral imaging micro-Raman biochip sensor module;

Biofluorescence LIDAR for triggers and stand-off detection of bioagents;

Micromachinized aerosol collectors; and Sensor network architectures. (NATIBO, 2001)

The following figure shows the biological detection system components as stated in the National Institute of Justice work entitled; "An Introduction to Biological Agent Detection Equipment for Emergency First Responders."

Biological Detection System Components

Source: National Institute of Justice (2001)

It is reported by the National Institute of Justice that the Department of Defense has a Hand-Held Sampling Kit which is a "prepackaged kit containing a panel of eight hand-held immunochromatographic assay (HHA) devices, a dropper bottle of buffer solution, two sterile cotton-tipped swabs and an instruction card." (National Institute of Justice, 2001) This HHA kit cannot be used to screen soil samples and as well cannot be used in screening surfaces that are heavy with dust. The DoD further has a "BioCapture BT-500 Air Sampler, a product developed by MesoSystems Technology, Inc. which is stated to incorporate the BioVIC Aerosol Collector and is a "hand-held battery-powered air sampler that collects airborne sampler for quantifying concentration levels." (National Institute of Justice, 2001)

Crisis Management

The National Institute of Justice states that "Emergency first responders (fire and rescue) will be involved in the early stages of crisis management, primarily the reporting of the use of a biological weapon. For this reason emergency first responders need to have an emergency response plan in place for any possible biological incident." (National Institute of Justice, 2001) the National Institute of Justice states that presently there is a lack in detection equipment for biological agents that is affordable which requires that first responders "integrate their response into the overall national effort." (National Institute of Justice, 2001) Emergency responders are advised to contact their nearest public health laboratory in the state in which they are located in order to make a determination of points of contact in the case of a biological warfare agent crisis.

The work entitled: Development of Models for Emergency Preparedness: Personal Protection Equipment, Decontamination, Isolation/Quarantine and Laboratory Capacity states: "The presentation of contaminated patients seeking treatment at local health care facilities is not a new concept. Every day, health care facilities are presented with patients who are exposed to chemicals from industrial accidents and agricultural chemical incidents. Additionally, acute and chronically ill patients frequently present to health care facilities with possible contagious pathogens requiring that appropriate control…