Abstract: Techniques and devices are disclosed for detecting particle composition. In one aspect, a method performed by a detector to detect particles includes receiving particles at an aerosol inlet of the detector. The method includes carrying the received particles within a stream of gas and charging the particles within the stream of gas using a charger to have a charge. The method includes transporting the charged particles to a location of a collection electrode. The method includes biasing the collection electrode to a voltage using a high-voltage supply to attract either negatively or positively charged particles, and analyzing the particles.

Abstract: The various embodiments described herein significantly increase charge probabilities of nanoparticles by first growing them to larger droplets using a diethylene glycol-based preconditioner, neutralizing the droplets with a bipolar charger, and then removing the condensed liquid to recover the original aerosol particles. The small droplet size is an important element in reducing the amount of aerosol particles with more than one charge. The high single-charge particle probability significantly enhances the monodisperse aerosol throughput of a DMA, while the reduced multiple charge probabilities ensure high monodispersity of DMA-classified aerosols and good data quality of SMPS measurements.

Abstract: A system and a method of measuring a particle's size in a select aerosol using the optical diameter of the particle to perform a mobility and/or aerodynamic diameter conversion without any knowledge about the particle's shape and its optical properties in the aerosol being characterized. In one example embodiment of the invention, the method includes generating a set of calibration data and finding the optimal refractive index and shape that best fits the calibration data. In addition, the method includes creating a new calibration curve that provides a mobility-equivalent or aerodynamic-equivalent diameter.

Abstract: A system and a method is described herein for the collection of small particles in a concentrated manner, whereby particles are deposited onto a solid surface or collected into a volume of liquid. The collected samples readily interface to any of a number of different elemental, chemical, or biological or other analysis techniques.

Abstract: A test accessory for testing a variety respirators. The accessory is designed to compliment existing equipment to provide a robust assessment of respirator performance. The accessory may include a head form having an inflatable bladder capable of fitting a variety of sizes of respirator masks. In some embodiments, the inflatable bladder does not rely on adhesives to effect a seal, thereby eliminating manufacturing and quality assurance steps. The test accessory may also include a detachable instrumentation module that may be removed from the accessory, enabling calibration and maintenance at a remote facility without need for transporting the entire unit. The module may also house a memory device that may be upgraded with calibration data and firmware during the calibration process.

Abstract: A test accessory for testing a variety respirators. The accessory is designed to compliment existing equipment to provide a robust assessment of respirator performance. The accessory may include a head form having an inflatable bladder capable of fitting a variety of sizes of respirator masks. In some embodiments, the inflatable bladder does not rely on adhesives to effect a seal, thereby eliminating manufacturing and quality assurance steps. The test accessory may also include a detachable instrumentation module that may be removed from the accessory, enabling calibration and maintenance at a remote facility without need for transporting the entire unit. The module may also house a memory device that may be upgraded with calibration data and firmware during the calibration process.

Abstract: A High Performance Liquid Chromatography (HPLC) system including a pressure reducer assembly for reducing pressurized streams to ambient pressure. The pressure reducer assembly includes first and second flow restrictors, each coupled to a common chamber that acts as a surge suppressor that mitigates pressure spikes in the discharge lines. The flow restrictors may comprise tubes having a high length-to-diameter ratio. The pressure losses through the flow restrictors, in combination with transition losses as the flow stream enters and exits the chamber, are sufficient to reduce a discharge stream from a specified inlet pressure to substantially ambient pressure, thus eliminating the need for pressurized waste containers.

Abstract: A hand-held, automated qualitative fit tester (QLFT) for establishing gas mask fit integrity. The automated QLFT may be configured to utilize a pressure source in combination with a cartridge and a nebulizer to generate aerosols having size distributions and concentrations that are substantially the same as OSHA-approved manual units. The QLFT may further include a cartridge that contains the aerosol solution used to test mask integrity. The cartridge may be configured to recapture solution that collects on the interior walls of the nebulizer. The automated QLFT may also be equipped with a microprocessor for executing sequences that are in substantive compliance with 29 CFR 1910.134 and for writing to a data storage device. The automated aspects of the invention can reduce or negate the need for operating personnel to repeatedly and manually actuate a squeeze ball and record results manually, as is required with present OSHA-approved hand-held aerosol generators.

Abstract: A respirator leak detection system and method for increasing the sensitivity and accuracy of leak detection through the fit seal of a respirator. A charged particle separator is used to separate charged particles that pass therethrough and to draw charged particles away from an aerosol flow into a clean gas flow. The separator may also be configured as an aerosol concentrator that takes in a major aerosol flow and outputs a minor flow of higher particle concentration. Neutral particles having no charge, which may have passed through the filtering medium respirator and which are not indicative of fit seal leaks are not entrained in the output flow for subsequent detection, thus increasing the accuracy of the filter leak detection system.

Abstract: A system for measuring size segregated mass concentration of an aerosol. The system includes an electromagnetic radiation source with beam-shaping optics for generation of a beam of electromagnetic radiation, an inlet sample conditioner with adjustable cut-size that selects particles of a specific size range, and an inlet nozzle for passage of an aerosol flow stream. The aerosol flow stream contains particles intersecting the beam of electromagnetic radiation to define an interrogation volume, and scatters the electromagnetic radiation from the interrogation volume. The system also includes a detector for detection of the scattered electromagnetic radiation an integrated signal conditioner coupled to the detector and generating a photometric output, and a processor coupled with the conditioner for conversion of the photometric output and cut-size to a size segregated mass distribution.

Abstract: An instrument for non-invasively measuring nanoparticle exposure includes a corona discharge element generating ions to effect unipolar diffusion charging of an aerosol, followed by an ion trap for removing excess ions and a portion of the charged particles with electrical mobilities above a threshold. Downstream, an electrically conductive HEPA filter or other collecting element accumulates the charged particles and provides the resultant current to an electrometer amplifier. The instrument is tunable to alter the electrometer amplifier output toward closer correspondence with a selected function describing particle behavior, e.g. nanoparticle deposition in a selected region of the respiratory system. Tuning entails adjusting voltages applied to one or more of the ion trap, the corona discharge element and the collecting element. Alternatively, tuning involves adjusting the aerosol flow rate, either directly or in comparison to the flow rate of a gas conducting the ions toward merger with the aerosol.

Abstract: An attenuated soft x-ray neutralizer for neutralizing aerosols. The apparatus includes a soft x-ray emitter that emits soft x-rays into an aerosol conditioning chamber. An attenuating window may be included that reduces the intensity of the soft x-rays that bombard the aerosol, thus generating fewer radiolytically generated particles. Another way to reduce or control the intensity of the soft x-rays is to control emission of the cathode in the soft x-ray emitter. The reduced intensity of the soft x-rays was found by experiment to satisfactorily condition an aerosol stream without substantial radiolytic generation of particles precipitation.

Abstract: A system is disclosed for condensation particle counting in conjunction with modifying an aerosol to enhance the formation and growth of droplets of a selected working fluid, preferably water. Before saturation with the working fluid, the aerosol is exposed to an aerosol modifying component, preferably a vapor including molecules that are adsorbed onto surfaces of the particles or other elements suspended in the aerosol. Adsorption alters the surface character of the suspended elements towards increased affinity for the vapor of the working fluid, to promote the formation and growth of working fluid droplets. The droplets are optically detected to indicate numbers and concentrations of the suspended elements.

Abstract: A method for identifying and determining the frequency of scattered radiation fringe patterns for applications such as particle or droplet sizing and laser Doppler velocimetery. The method utilizes a series of windowed Fourier transforms performed on an intensity profile of the scattered radiation to locate a segment where a fringe pattern is located on the intensity profile. A standard Fourier transform is then performed on the segment to determine a dominant frequency of the fringe pattern, from which a physical quantity such as diameter or velocity of the particle or droplet may be derived. The method may be utilized with a line or an array sensor to measure the fringe patterns in a spatial domain, or with a point detector to measure the fringe patterns in the time domain.

Abstract: An instrument for non-invasively measuring nanoparticle exposure includes a corona discharge element generating ions to effect unipolar diffusion charging of an aerosol, followed by an ion trap for removing excess ions and a portion of the charged particles with electrical mobilities above a threshold. Downstream, an electrically conductive HEPA filter or other collecting element accumulates the charged particles and provides the resultant current to an electrometer amplifier. The instrument is tunable to alter the electrometer amplifier output toward closer correspondence with a selected function describing particle behavior, e.g. nanoparticle deposition in a selected region of the respiratory system. Tuning entails adjusting voltages applied to one or more of the ion trap, the corona discharge element and the collecting element. Alternatively, tuning involves adjusting the aerosol flow rate, either directly or in comparison to the flow rate of a gas conducting the ions toward merger with the aerosol.

Abstract: Particle analyzing systems with fluorescence detection are disclosed, primarily in connection with particle sizing based on scattered light intensity or time-of-flight measurement. In one system, emission of fluorescence is used as a threshold for selecting particles for further analysis, e.g. mass spectrometry. In another embodiment, laser beams arranged sequentially along an aerosol path are selectively switched on and off, to increase the useful life of components, and diminish the potential for interference among several signals. Other embodiments advantageously employ color discrimination in aerodynamic particle sizing, single detectors positioned to sense both scattered and emitted fluorescent radiation, and laser beam amplitude or gain control to enhance the range of fluorescence detection.

Abstract: A system is disclosed for condensation particle counting in conjunction with modifying an aerosol to enhance the formation and growth of droplets of a selected working fluid, preferably water. Before saturation with the working fluid, the aerosol is exposed to an aerosol modifying component, preferably a vapor including molecules that are adsorbed onto surfaces of the particles or other elements suspended in the aerosol. Adsorption alters the surface character of the suspended elements towards increased affinity for the vapor of the working fluid, to promote the formation and growth of working fluid droplets. The droplets are optically detected to indicate numbers and concentrations of the suspended elements.

Abstract: An aerosol detector, particularly well suited for liquid chromatography applications, includes a corona discharge source controlled to selectively charge the non-volatile residue particles of an aerosol. The aerosol initially is composed of droplets of a liquid sample, with the residue particles resulting from droplet evaporation. The selectively charged residue particles, each carrying a charge in proportion to its size, are collected at a conductive filter. The electrical current along a conductor coupled to the filter is measured repeatedly or continuously to provide an indication of concentrations of the non-volatile material. Preferably, a pneumatic nebulizer is used to generate the aerosol. When used in a liquid chromatography system, the detector can yield several separated areas of relatively high electrical current, corresponding to concentrations of several different analytes in the liquid sample.

Abstract: A system for analyzing aerosols incorporates a corona discharge ion generator with a positively or negatively charged corona discharge needle formed of platinum or a platinum alloy. A high speed (40-210 meter per second) air flow sweeps the ions away from the corona discharge, and propels the ions into a mixing chamber in a turbulent jet that encounters an aerosol, also provided to the mixing chamber. In one version of the ion generator, the ions are carried into the mixing chamber through an orifice formed in a positively or negatively biased plate. In another alternative, the aerosol droplets are electrostatically generated, and propelled into the mixing chamber as an aerosol jet that confronts the ion jet to enhance a mixing of the charged droplets and the ions. In this version the droplets are advantageously neutralized to leave predominantly singly charged positive and negative particles, to provide a neutralized aerosol particularly well suited for analysis with a mass spectrometer.

Abstract: An apparatus for classifying polydisperse aerosols includes aerosol and sheath gas conduits for conducting a sample aerosol and a sheath gas toward a merger area. At the merger area the sheath gas and about ten percent of the sample aerosol merge, then travel through a differential mobility analyzer (DMA) and along a tubular electrode of the DMA. Selected particles, i.e. particles having electrical mobilities within a narrow range, pass through a collection aperture of the electrode. The DMA output, an aerosol consisting of the selected particles, is provided to a condensation particle counter or other device for determining the aerosol concentration. The remainder of the sample aerosol is conducted away from the merger area along a bypass flow conduit. The bypass flow and an improved aerodynamic design provide for a slit at the merger area that is sufficiently narrow to minimize unwanted electric field penetration at the slit and DMA entrance.