Patent Application
20170273845
The present disclosure relates to a system and method for reducing airborne contaminants in an indoor space.
Individuals suffering from a microbial infection (e.g., a bacterial, viral, or fungal infection) or a communicable disease are commonly admitted to a hospital for evaluation and treatment. These infected patients present a risk that they may spread and transmit their infection to other patients in the hospital. Airborne microbes are commonly spread through the central heating, ventilation, and air conditioning (HVAC) system in the hospital. For instance, a patient infected with a respiratory illness may expel microbes into the air by coughing or sneezing and these airborne microbes may then be circulated throughout the hospital by the HVAC system. Accordingly, many hospitals have retrofitted or outfitted their HVAC systems with filters designed to reduce the spread of contaminants throughout the hospital.
However, positioning the filters in the HVAC system limits the efficacy of the filters at reducing airborne microbes because the filters are remote from the source of the airborne microbes (e.g., an infected patient). Additionally, the air is typically cycled through the HVAC filters at a relatively slow rate, which further limits the efficacy of conventional filters in reducing the overall microbial load in the hospital. For instance, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 170-2008 recommends six air exchanges per hour in a standard hospital patient room and ten air exchanges per hour in a standard bathroom in a hospital patient's room. A single air exchange occurs when the total volume of air in a room has been processed and/or treated once by the filtration system. Additionally, conventional filters in central HVAC systems are single pass systems because the air is passed through the HVAC system only once before being distributed throughout the building, which further limits the efficacy of these conventional HVAC filters.
Embodiments of the present disclosure are directed to various methods for reducing airborne contaminants (e.g., airborne microbes) in an indoor space or area. In one embodiment, the method includes positioning a portable photo-catalytic oxidation (PCO) system proximate a source of contaminants in the indoor space and activating the PCO system to circulate air through the PCO system at a rate sufficient to perform from approximately 16 to approximately 32 air exchanges per hour in the indoor space. The PCO system is configured to oxidize contaminates in the air. The indoor space may be a hospital room and positioning the PCO system may include positioning the PCO system proximate a patient's hospital bed in the hospital room. Positioning the PCO system may include positioning the PCO system proximate a foot of the patient's hospital bed. Positioning the PCO system may include positioning the PCO system between the hospital bed and an entrance door of the hospital room. Positioning the PCO system may include positioning the PCO system between the hospital bed and a return air duct in the hospital room. The PCO system may have an airflow capacity of at least approximately 500 cubic feet per minute (CFM) and the indoor area may have a volumetric size from approximately 935 ft3 to approximately 1875 ft3. The indoor area may be an open system. The PCO system may include a support medium having a minimum efficiency reporting value (MERV) rating from approximately 10 to approximately 12 and a photocatalyst on the support medium. The support medium may be pleated and may be a fibrous matte. The photocatalyst may be titanium dioxide and may also include platinum.
Embodiments of the present disclosure are also directed to various systems for reducing airborne contaminants (e.g., airborne microbes) in an indoor space or area. In one embodiment, the system includes a portable photo-catalytic oxidation (PCO) system proximate a source of contaminants in the indoor space. Activation of the PCO system is configured to circulate air through the PCO system at a rate sufficient to perform approximately 16 to approximately 32 air exchanges per hour in the indoor space. The PCO system is configured to oxidize contaminants in the air. A ratio of an airflow capacity of the PCO system to a volumetric size of the indoor space may be from approximately 0.25 to approximately 0.5. The indoor space may have a volumetric size from approximately 935 ft3 to approximately 1875 ft3. The PCO system may have an airflow capacity of at least approximately 500 cubic feet per minute. The indoor space may be an open system hospital room. The PCO system may include a support medium having a minimum efficiency reporting value (MERV) rating from approximately 10 to approximately 12 and a photocatalyst on the support medium. The support medium may be pleated and may be a fibrous matte. The photocatalyst may be titanium dioxide and may also include platinum. The PCO system may be proximate a foot of a hospital bed in a hospital room, may be positioned between the hospital bed and an entrance door of the hospital room, and/or may be positioned between the hospital bed and a return air duct in the hospital room.
This summary is provided to introduce a number of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in limiting the scope of the claimed subject matter.
These and other features and advantages of embodiments of the present disclosure will become more apparent by reference to the following detailed description when considered in conjunction with the following drawings. In the drawings, like reference numerals are used throughout the figures to reference like features and components. The figures are not necessarily drawn to scale.
The present disclosure relates to various methods of reducing airborne contaminants, such as airborne microbes (e.g., bacteria, viruses, and/or fungi), in a room or other indoor space (e.g., a hospital room, a home, a store, an office building, an airplane cabin, a cruise line, or a transportation vehicle) with a photo-catalytic oxidation (PCO) system. The circulation rate of the air through the PCO system and the proximity of the PCO system to a patient infected with a microbial infection or a communicable disease may be selected to optimize the efficacy of the PCO system in reducing the overall microbial load in the room. Reducing the microbial load in the room mitigates the risk that the airborne microbes will spread and infect other individuals. For instance, the methods of the present disclosure may be used to reduce the incidence of healthcare associated infections (HAI), which are infections acquired by patients during the course of receiving healthcare treatment for an unrelated ailment or condition. Additionally, the methods of the present disclosure may include positioning the PCO system proximate the source of the airborne microbes and operating the PCO system as a multi-pass system in which the air is repeatedly treated before the air is recirculated throughout the building.
With reference now to
With continued reference to the embodiment illustrated in
With reference now to the embodiment illustrated in
In one embodiment, the volumetric size of the room 101 and the airflow capacity of the PCO system 100 may be selected such that the PCO system 100 is sufficiently sized relative to the hospital room 101 to perform from approximately 16 to approximately 32 air exchanges per hour, such as, for instance, approximately 24 air exchanges per hour. The airflow capacity of the PCO system 100 is a function of the fan speed, the size of the PCO filter 111, and the air permeability rating (“APR”) of the PCO filter 111, described below. A single air exchange occurs when the total volume of air in the room 101 has been treated once by the PCO system 100. For instance, in an embodiment in which the PCO system 100 is operating at an airflow capacity of approximately 500 ft3/min and the room 101 has a volumetric size of approximately 1250 ft3, the PCO system 100 is configured to perform approximately 24 air exchanges per hour. In one embodiment, a ratio of the airflow capacity of the PCO system 100 to the volumetric size of the room 101 may be from approximately 0.25 to approximately 0.55, such as, for instance, approximately 0.4 (e.g., the PCO system 100 may be positioned in a room 101 having a volumetric size such that the PCO system 100 is configured to perform from approximately 0.25 to approximately 0.55 air exchanges per minute). In one embodiment, the method may include operating the PCO system 100 in a room 101 having a volumetric size from approximately 935 ft3 to approximately 1875 ft3. In one or more alternate embodiments, the airflow capacity of the PCO system 100 and the size of the room 101 in which the PCO system 100 is operating may be selected such that the PCO system 100 is configured to perform any other suitable number of air exchanges per hour depending on a variety of factors, including the desired rate of oxidation (i.e. degradation) of the VOCs and airborne microbes in the air and the initial microbial load in the room 101.
The support medium 112 may be a silica-based fibrous matte (e.g., fiberglass) or other suitable support material to which the photocatalyst 113 is adhered. The photocatalyst 113 may be adhered to the support medium 112 in any suitable manner, such as, for example, as described in U.S. Pat. Nos. 5,766,455 and 5,834,069, the entire contents of both of which are hereby incorporated by reference. The photocatalyst 113 on the support medium 112 may be a semiconductor catalyst such as a transition metal oxide, for example titanium dioxide or other suitable material. Additionally, the photocatalyst 113 may be metalized or non-metalized. The photocatalyst 113 may be metalized with any suitable metal such as, for example, a noble metal, such as platinum and/or palladium. The addition of platinum on the photocatalyst 113 is configured to accelerate the oxidation process. The metal may be deposited on the photocatalyst 113, if desired, before the photocatalyst 113 is applied to the support medium 112.
In one embodiment, the support medium 112 has a minimum efficiency reporting value (MERV) rating in a range from approximately 10 to approximately 12, although in one or more alternate embodiments, the support medium 112 may have any other suitable MERV rating. Additionally, in one embodiment, the support medium 112 is composed of loosely-packed fibers such that the support medium 112 has an air permeability rating (“APR”) of greater than approximately 155 CFM/ft2, such as, for instance, at least approximately 200 CFM/ft2 or at least approximately 247 CFM/ft2. Loosely packing the fibers of the support medium 112 is configured to reduce the pressure drop of the air across the support medium 112, which allows the air to pass more quickly through the support medium 112. The increased rate of air circulation through the PCO system 100 exposes the airborne microbes or other contaminants in the air to the active photocatalyst sites on the support medium 112 more frequently, and thus the airborne microbes or other contaminants are oxidized (i.e., degraded) more rapidly than with an otherwise comparable PCO filter having a lower air permeability rating. In one or more alternate embodiments, the support medium 112 may be composed of densely-packed fibers such that the support medium 112 has an APR of approximately 155 CFM/ft2 or less.
With continued reference to the embodiments illustrated in
Tests were performed to determine the efficacy of the methods of the present disclosure in reducing airborne microbial loads. The PCO systems 100 of the present disclosure were placed proximate the foot 103 of hospital beds 104 in a number of patient rooms within one emergency department that housed fifty different patients over the course of the testing period. Prior to activating the PCO systems 100, the air in each room 101 was tested to establish the baseline microbial load in each of the rooms 101. The baseline air sampling was performed using three 6-stage Andersen samplers positioned at the head 105 and the foot 103 of the hospital beds 104 and at an exit/entrance doorway 119 of each hospital room 101. The air samples were collected on blood agar plates.
Following completion of the baseline air sampling, the PCO systems 100 proximate the foot 103 of the hospital beds 104 were activated to circulate the contaminated air 116 in the room 101 through the PCO system 100. The air 116 was circulated through the PCO system 100 for approximately 20 minutes before beginning air sampling to determine the reduction in microbial load in the rooms 101. In one embodiment, the PCO system 100 had a maximum capacity of approximately 500 ft3/minute and the rooms 101 had a volumetric size of approximately 1250 ft3 such that approximately 8 air exchanges occurred within the 20-minute period prior to sampling (i.e., a rate of approximately 24 air exchanges per hour). A single air exchange occurs when the total volume of air in the room 101 has been treated once by the PCO system 100. After the air 116 was treated by the PCO systems 100 for approximately 20 minutes, the air was sampled again with the three 6-stage Anderson samplers in each room 101. Once the samples were collected, the blood agar plates were removed from the Anderson samplers and placed in an incubator at approximately 37° C. The plates were incubated for approximately 48 hours and then the number of colonies formed on the agar plates were calculated and recorded.
The results of the tests are summarized below in Table 1. For each location, the colony count was summed across the 6 stages of the Anderson samplers. The results are presented as median values across each of the tested rooms and as interquartile ranges (i.e., the 25th and 75th quartiles) shown in parentheses following the median value. Table 1 also indicates the number of patients (N) whose rooms were sampled for each of the three locations of the PCO system 100 in the room 101. The p-values were determined using the signed Wilcoxon rank-sum test.
Accordingly, operation of the PCO systems 100 at the feet 103 of the hospital beds 104 for approximately 20 minutes reduced the microbial load at the heads 105 of the hospital beds 104 by approximately 54.2%. Operation of the PCO systems 100 at the feet 103 of the hospital beds 104 for approximately 20 minutes also reduced the microbial load at the feet 103 of the beds 104 by approximately 46.9% and at the exit/entrance doors 119 of the rooms 101 by approximately 26.7%. The lower reduction in the microbial load at the exit/entrance door 119 may be due to higher personnel traffic and activity through and/or around the exit/entrance door 119 of the room 101 compared to the foot 103 and the head 105 of the hospital beds 104. That is, unlike a clean room or other sterile controlled environments, the patient rooms 101 were open systems in which personnel and other individuals were permitted to freely enter and exit the rooms 101 through the doorway 119 during the tests.
Although in one or more embodiments the PCO systems 100 of the present disclosure may be used to reduce airborne contaminants (e.g., airborne microbes) in a hospital room, in one or more embodiments, the PCO systems 100 of the present disclosure may be used to reduce airborne contaminants, such as airborne microbes (e.g., bacteria, viruses, and/or fungi), in any other type of room or other indoor space or area, such as, for instance, in homes, stores, office buildings, airplane cabins, cruise lines, and transportation vehicles (i.e., the PCO systems 100 of the present disclosure may be used in any indoor space in which airborne contaminants are desired to be reduced).
While this invention has been described in detail with particular references to exemplary embodiments thereof, the exemplary embodiments described herein are not intended to be exhaustive or to limit the scope of the invention to the exact forms disclosed. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of assembly and operation can be practiced without meaningfully departing from the principles, spirit, and scope of this invention, as set forth in the following claims. Although relative terms such as “outer,” “inner,” “upper,” “lower,” “below,” “above,” “vertical,” “horizontal,” and similar terms have been used herein to describe a spatial relationship of one element to another, it is understood that these terms are intended to encompass different orientations of the various elements and components of the invention in addition to the orientation depicted in the figures. Additionally, as used herein, the term “substantially” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Moreover, the tasks described above may be performed in the order described or in any other suitable sequence. Additionally, the methods described above are not limited to the tasks described. Instead, for each embodiment, one or more of the tasks described above may be absent and/or additional tasks may be performed. Furthermore, as used herein, when a component is referred to as being “on” another component, it can be directly on the other component or components may also be present therebetween. Moreover, when a component is referred to as being “coupled” to another component, it can be directly attached to the other component or intervening components may be present therebetween.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/046996 | 8/26/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62041992 | Aug 2014 | US |
