Ventilation – Having forced recirculation – Including automatic control means
Reexamination Certificate
2003-03-28
2004-09-28
Lu, Jiping (Department: 3749)
Ventilation
Having forced recirculation
Including automatic control means
C454S233000, C454S236000, C454S239000
Reexamination Certificate
active
06796896
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to an environmental control unit for use in air handling systems that provides air conditioning, heating, and high efficiency airborne toxic agent filtration equipment and functions in a single unitary packaged unit, and, in particular, relates to a unitary packaged unit providing heating, ventilation and/or air conditioning of an air supply provided to an enclosure as well as protecting the occupant(s) and equipment in the enclosure against external or internal airborne release of toxic chemical, biological, or radiological agents that threaten to contaminate the air supply. It also relates to an air handling method and system providing CBR filtering for the airspace of a shelter or safe room.
BACKGROUND OF THE INVENTION
There is an ever-increasing need for air handling systems that include air filtration systems that can be deployed to protect an enclosure against noxious airborne agents released in the vicinity of the enclosure. Every year there are numerous incidents of noxious fumes entering buildings and causing illness and disruptions due to accidents or malicious pranks. There now is heightened concern about super-toxic airborne agents being released as part of a nuclear, biological or chemical (“NBC”) attack launched by terrorists in a metropolitan area or as directed against a particular governmental, public or private building or structure. In addition, military personnel in combat areas may need protection from enemy releases of airborne chemical, biological, and radiological (“CBR”) agents in the vicinity of a tent or other enclosure area where the troops are bivouacked or have set up a field command or field hospital, and so forth. Whether a civilian or military setting, a typical air handling system for an enclosure will be served by ductwork connecting airflow between the enclosure and a remote HVAC (“heating, ventilating, and air conditioning”) unit. The HVAC system is normally used to adjust the temperature of the airflow and circulate the air to and from one or more enclosures.
Standard dust filters are ineffective against CBR agents. Standard dust filters, such as cardboard framed fiberglass matt filters, have relatively low efficiency rates for removing for dust and particles, and are not useful for removing pollen, microorganisms, smoke, or gases. Commercially available electrostatic fiber filters have higher efficiencies than standard dust filters and can remove pollens and other small solid particulates, but they can not intercept and remove gases. HEPA (“High-Efficiency Particulate Air”) filters are known that are used for high-efficiency filtration of airborne dispersions of ultrafine solid and liquid particulates such as dust and pollen, radioactive particle contaminants, and aerosols. For example, for removal of non-toxic aerosols, HEPA filters are typically used as the sole filtration element. The efficiency of a HEPA filter is standardized as being at least 99.97% for particles of dioctylphthalate (DOP) having a size of 0.3 microns in diameter. The airflow resistance of conventional HEPA filters is typically about one (1) inch, water gauge (iwg) at 500 feet per minute (FPM) approach velocity. This resistance increases steadily as the HEPA filter loads with dust or other fine particles in service. However, where the threat is a gaseous chemical compound or a gaseous particle of extremely small size (i.e., <0.001 microns), the conventional commercially-available HEPA filters can not intercept and control those types of airborne agents. In addition, the vast majority of prior air handling systems have not been designed nor were designable to accommodate the large increase in airflow resistance that would be associated with use of a conventional HEPA filter.
The most commonly found filter technology used to filter gaseous substances and materials from an airflow is based on activated carbon. CBR filtering has been previously implemented in certain applications, such as in gas masks or in industrial processes, by using filter beds of activated impregnated carbons or other sorbents for ultra-high-efficiency filtration of super toxic chemical vapors and gases from an air or gas stream passed through the filter. Commercial filters of this sort generally include activated carbon loaded nonwovens, in which the activated carbon is bonded to a nonwoven fiber mat. Carbon filters used for protection against toxic chemicals are typically designed to maintain an efficiency of at least 99.999% removal of airborne particulates. An activated carbon filter typically functions by removing molecules from an air stream by adsorption in which molecules are entrapped in pores of the carbon granules. Activated carbon is an effective sorbent for removal of a wide range of chemical vapors due to its extensive microporosity and broad range of pore sizes. In order to filter high vapor pressure chemicals, impregnants are added to the activated carbon. The impregnants react with the gas passing through the filter to form products that are captured by the filter or rendered innocuous. The pressure drop of high-efficiency carbon filters may range from about 1 to 6 iwg at 250-500 FPM approach velocity. These carbon filters also have been used in combination with a HEPA filter.
Activated carbons are useful in respirators, collective filters and other applications, and often involved the use of special impregnates to remove gases that would not otherwise be removed through the use of unimpregnated activated carbons. These impregnated activated carbon adsorption for removal of toxic gases and/or vapors have been known and used for many years. The prior art formulations often contain copper, chromium and silver impregnated on an activated carbon. These absorbents are effective in removing a large number of toxic materials.
For example, it is known that removal of highly toxic chemicals such as cyanogen chloride, hydrogen cyanide and cyanogen can be achieved with the presence of chromium and copper on the activated carbon. Copper and silver impregnants have been shown to be effective in the removal of arsine and phosphine. Chlorine, hydrogen chloride, hydrogen fluoride and hydrogen sulfide are also removed by the presence of copper impregnants on activated carbon.
In addition to a number of other inorganic materials, which have been impregnated on activated carbon, various organic impregnants have been found useful in military applications for the removal of cyanogen chloride. Examples of these include triethylenediamine (TEDA) and pyridine-4-carboxylic acid. In the nuclear industry, the impregnation of charcoal absorbents with triethylenediamine (TEDA) has led to an improved adsorbent with excellent performance in the monitoring and trapping of radioactive iodine and methyl iodide from the off-gases of nuclear reactors The same technology has been extended to the treatment of military charcoal used in respirators for improved protection against small, volatile super-toxic compounds, such as cyanogen chloride, which normally do not adsorb on the charcoal surface to any significant extent.
Various types of high-efficiency filter systems, both commercial and military systems, have been proposed for building protection using ASZM-TEDA carbon for filtering a broad range of toxic chemical vapors and gases. These filter systems have been proposed for integration into the HVAC system of new construction. However, conventional air handling units are not designed to accommodate a large increase in airflow resistance that an activated carbon filter would add. In addition, conventional air handling units have dust filter slots that permit relatively high bypass around the filter media, which not only reduced the overall efficiency of the HEPA filters but also is unacceptable where toxic airborne agents must be entrapped.
FIG. 1
illustrates a conventional HVAC system
100
having limited CBR (“chemical, biological and radiological”) filtering capability. An air intake/blower unit
11
incorporates a CBR filtration apparatus. Ideally, such
Fitch Even Tabin & Flannery
Lu Jiping
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