Measuring and testing – Sampler – sample handling – etc. – With constituent separation
Reexamination Certificate
2000-11-30
2003-04-22
Williams, Hezron (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
With constituent separation
C073S863230
Reexamination Certificate
active
06550347
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method of collecting and concentrating airborne particles, organic or inorganic gasses and microorganisms, and more particularly to an apparatus for collecting airborne components by impinging or impacting them into a fluid or liquid entrapment media.
2. Background Information
Airborne particles are commonly collected by (a) inertial impaction onto selected surfaces, (b) centrifugal force resulting from spinning collected air such that particles are forced to an outside wall or medium for collection or (c) impingement into liquid where particles are intended to remain suspended in liquid after air bubbles pass through and out of the collection liquid.
The practice of impingement of biological particles into liquid during long-term (2 hours) aerosol collection periods has a distinct advantage over dry collection methods, in that microorganisms are not stressed or killed due to dehydration during continuously moving airflow, which removes moisture from the microbial cells.
However, low concentrations of particles collected from aerosols into fluids often require concentration in order to enumerate and quantitate these particles more accurately. This concentration step generally involves removal of the fluid from the collector followed by filtration of the fluid through separate equipment containing a small (0.45-0.2 micron) pore sized membrane in order to collect and concentrate the microorganisms. These extra fluid removal and filtration steps are disadvantages of prior art collection systems.
Another disadvantage of utilizing impinger methods to collect air particles, including bacteria, includes reaerosolization of microbes by air bubbles continuously flowing through the impacted collection fluid. As bubbles rise to the surface of the collection fluid, especially when utilizing aqueous liquids, the bubbles burst and send tiny droplets of water into the air above the collection fluid. These droplets can contain the microbes which the collection fluid was intended to collect and retain. As these droplets and entrapped microbes flow through the collection vessel and are deposited on the exhaust or effluent air channel walls, the microorganisms can be directly or indirectly re-introduced into the ambient air from which they were previously collected. Worse, the reaerosolized microbes could be introduced into previously clean air outside the sampling area depending on where the effluent air from the collection unit is exhausted. Additionally, as liquid or fluid molecules are continuously removed from the impinger by these processes, the decreased volume of fluid causes a concentrating effect on the remaining particles or organisms trapped therein and increased numbers of microbes or other particles are removed within the subsequent air bubbles and resultant droplets. Eventually, the impinger liquid or fluid level may be lowered below the air inlet tube nozzles or passages, thereby defeating the purpose of the apparatus. This loss of entrapment fluid thus shortens the operational life of the sampler.
It is an object of the invention to provide an air sampler which prevents recontamination of a sampling environment by release of contaminants from the air sampler in the form of water droplets with entrained contaminants.
It is another object of the invention to provide an air sampler which has an improved counting accuracy due to preventing escape with the outlet air of particles and contaminants, and being able to rinse down the inside of the sample chamber to recapture all sampled particles.
It is a further object of the invention to provide an air sampler which uses a liquid or fluid entrapment media, with or without additive or components such as antibodies to specific particles, attached or unattached to specific media such as Latex or polystyrene or other organic or inorganic beads or similar particles for specific of general entrapment of components, contaminants and particulates, which also has a longer run time than prior art air sampling devices which utilize a liquid or other fluid as an entrapment media.
It is a further object of the invention to provide an air sampler which enables a higher flow of air through the air sampler due to less loss of entrapment fluid through the air outlet.
An additional object of the invention is to provide an air sampler in which entrapment fluid in the air sampler is drained from the air sampler through a filter which is sized to capture particulates from the entrapment fluid.
SUMMARY OF THE INVENTION
In the apparatus of the present invention, a collection vessel is provided which allows a measured airflow which can contain airborne particles to be impinged through liquid or other entrapment fluid. The air sampler is designed to separate particulates and components from the air. The particulates can include all manner of microbes, including bacteria, yeast, mold, airborne parasites, single cell organisms, and viruses. The particulates can also include such things as inorganic or organic dust or debris, pollen, spores, weed seed, and powders. As the air is passed through the entrapment fluid, the entrapment fluid can be designed to absorb gases of interest, such as carbon monoxide, methane, carbon dioxide, oxygen, ethylene, nitrogen, or any number of organic or inorganic air gaseous contaminants, including poisonous gases used in chemical warfare. All of these substances, microbes, particulates and gases or related substances are described as air components.
The device of the invention is an air sampler for collecting selected air components which are suspended or carried in the air. The air sampler includes a sample body for entrapment of particles or components contained in air. It also includes an air intake for admitting air with entrained particles from a sampling environment into the sampler body. Contained within the sampler body is an entrapment fluid which serves to entrap, collect and retain or capture the selected air component. An impinger tube is utilized for bringing air into the sampler body and below the surface of the entrapment fluid, and for releasing bubbles of air through the entrapment fluid. As the bubbles rise from the impinger tube through the entrapment fluid, particles in the air are attracted to the liquid entrapment fluid or components thereof, and are adsorbed, in the case of particles, or absorbed in the case of gases into the entrapment fluid. Air from the impinger tube exists the entrapment fluid as the bubbles reach the surface and burst. The sampler body is provided with an air outlet which is located above the upper liquid level of the entrapment fluid. A pump is provided which evacuates air from the sampler body, through the air outlet. The decreased pressure of air thus created above the entrapment fluid causes air to be drawn in through the impinger tube and through the air intake to replace the evacuated air above the entrapment fluid.
A hydrophobic vent filter is positioned above the upper level of the entrapment fluid, over the air outlet, so that before air enters the air outlet, it must pass through the hydrophobic filter. The hydrophobic filter is designed to prevent water or other polar or aqueous liquid droplets, with their entrained particles, from exiting from the sampler body through the air outlet. The hydrophobic filter is designed so that only molecular water, in the form of water vapor, is allowed to exit the air sampler. The hydrophobic vent filter may be a Teflon coated fibrous filter, or other hydrophobic material, or coated material such as a polytetrafluoroethylene (PTFE), or PTFE coated fibrous filter, or other type of filter, or selective screening material which allows air but not aqueous liquids to pass. After air components have been collected in the sampler body, the entrapment fluid can be removed for testing. If the selected air component of interest are microbes, the entrapment fluid may be filtered through a very fine filter which will separate out the microbes but allow the
Dykas Frank J.
Garber Charles D
Nipper Stephen M.
Shaver Robert L.
Williams Hezron
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