Air sanitization system with variable speed fan

An air sanitization system including a reactive oxygen species generator, a variable speed fan, a pathogen sensor and a controller. The reactive oxygen species generator generates reactive oxygen species from an oxygen-containing gas and discharges the reactive oxygen species to a conditioned space. The variable speed fan directs the oxygen-containing gas to the reactive oxygen species generator at a controlled speed. The pathogen sensor senses a level of airborne pathogens in the conditioned space and generates a signal indicative of the level of pathogens sensed. The controller receives the signal from the pathogen sensor and varies the speed of the variable speed fan in response to the signal to decrease a speed of the variable speed fan in response to an increase in the level of airborne pathogens sensed by the pathogen sensor.

BACKGROUND

The present invention relates to an air sanitization system generating ozone and other reactive oxygen species, and a control system therefor.

U.S. Patent Publication No. 2007/0154344 discloses a sterilizer unit that produces ozone for killing mold and viruses in an interior space. The temperature and relative humidity of the interior space are measured by sensors and are indicative of the favorability of growing conditions for the mold and viruses. A control unit determines a mode of operation based on the sensed temperature and relative humidity. For more favorable mold and virus growing conditions, the control unit increases ozone production and increases a speed of a blower unit to the ozone generator.

SUMMARY

In one embodiment, the invention provides an air sanitization system including a reactive oxygen species generator, a variable speed fan, a pathogen sensor and a controller. The reactive oxygen species generator generates reactive oxygen species from an oxygen-containing gas and discharges the reactive oxygen species to a conditioned space. The variable speed fan directs the oxygen-containing gas to the reactive oxygen species generator at a controlled speed. The pathogen sensor senses a level of airborne pathogens in the conditioned space and generates a signal indicative of the level of pathogens sensed. The controller receives the signal from the pathogen sensor and varies the speed of the variable speed fan in response to the signal to decrease a speed of the variable speed fan in response to an increase in the level of airborne pathogens sensed by the pathogen sensor.

In another embodiment, the invention provides a method of controlling an air sanitization system for sanitizing a conditioned space. The method includes generating short-lived reactive oxygen species in the reaction chamber, generating long-lived reactive oxygen species in the reaction chamber, passing a pathogen-containing gas through the reaction chamber to remove at least a portion of pathogens from the pathogen-containing gas, distributing the long-lived reactive oxygen species to the conditioned space and onto surfaces in the conditioned space, sensing an amount of pathogens in the pathogen-containing gas, increasing a dwell time of a portion of the pathogen-containing gas within the reaction chamber in response to an increase in the amount of pathogens sensed to increase exposure of the pathogens to the short-lived reactive oxygen species, and decreasing the dwell time of a portion of the pathogen-containing gas within the reaction chamber in response to a decrease in the amount of pathogens to increase distribution of long-lived reactive oxygen species to the conditioned space for sanitizing the surfaces.

In yet another embodiment, the invention provides an air sanitization system. The air sanitization system includes a reactive oxygen species generator, a variable speed fan, a pathogen sensor, and a controller. The reactive oxygen species generator generates reactive oxygen species from an oxygen-containing gas and discharges the reactive oxygen species to a conditioned space. The variable speed fan directs the oxygen-containing gas to the reactive oxygen species generator at a controlled speed. The pathogen sensor senses a level of airborne pathogens in the conditioned space and generates a signal indicative of the level of pathogens sensed. The controller receives the signal from the pathogen sensor and varies the speed of the variable speed fan in response to the signal to decrease a speed of the variable speed fan in response to an increase in the level of airborne pathogens sensed by the pathogen sensor and to increase the speed of the variable speed fan in response to a decrease in the level of airborne pathogens sensed by the pathogen sensor. The controller decreases the fan speed by a predetermined percentage when the level of airborne pathogens is greater than or equal to a predetermined maximum level of airborne pathogens. The controller increases the fan speed by another predetermined percentage when the pathogen level is less than or equal to a predetermined minimum level of airborne pathogens. The reactive oxygen species include at least ozone and vapor phase hydrogen peroxide, and the ozone and vapor phase hydrogen peroxide are delivered to the conditioned space to provide surface and air decontamination.

DETAILED DESCRIPTION

FIG. 1illustrates an air sanitization system10for sanitizing air and surfaces of a conditioned space12. The air sanitization system10has a reaction chamber14having an inlet18and an outlet22, a reactive oxygen species (ROS) generator26housed within the reaction chamber14and positioned between the inlet18and outlet22, and a variable speed fan30positioned to deliver a variable speed flow of pathogen- and oxygen-containing gas to the inlet18of the reaction chamber14. The outlet22is coupled to a diffuser34for distributing cleaned air and reactive oxygen species to the conditioned space12.

The ROS generator26preferably includes a dielectric barrier discharge (DBD) plasma generator, such as the ROS generator described in U.S. Patent Application Publication No. 2007/0119699, filed Nov. 30, 2005, which is incorporated by reference herein. The ROS generator26generates reactive oxygen species from an oxygen-containing gas. Reactive oxygen species oxidize pollutants to effectively remove them from the air and surfaces. Reactive oxygen species include one or more of oxygen ions, free radicals, organic and inorganic peroxides, ozone, and other reactive oxygen species, some of which are long-lived and some of which are short-lived. For example, hydroxide and nitric oxide are short-lived reactive oxygen species, and vapor phase hydrogen peroxide and ozone are long-lived reactive oxygen species. The long-lived ROS survive to be distributed into the conditioned space12, while the short-lived ROS are active substantially within the reaction chamber14. In other constructions, other types of ROS generators may be employed.

The variable speed fan30is positioned adjacent the inlet18of the reaction chamber14and delivers a flow of pathogen- and oxygen-containing gas from the conditioned space12to the ROS generator26to be converted into reactive oxygen species and cleaned. The fan30is operable at multiple speeds and is preferably operable at one- or five-percent increments of speed between zero and 100% full speed. In other constructions, the variable speed fan30may be positioned elsewhere upstream or downstream of the ROS generator26to direct gas to the ROS generator26, and other types of variable speed fans capable of being controlled to operate at multiple speeds may also be employed.

The diffuser34is coupled to the outlet22of the reaction chamber14for directing an output gas from the reaction chamber14into the conditioned space12. The output gas includes cleaned air and reactive oxygen species containing primarily long-lived ROS generated by the ROS generator26. The diffuser34includes multiple outlets38for distributing the output gas to various locations within the conditioned space12, preferably for even, or nearly even, distribution. In other constructions, the distribution of the output gas can be distributed unevenly by the diffuser. In yet other constructions, other types of diffusers may be employed, and in other constructions still, no diffuser may be employed.

A pathogen sensor42is positioned in the conditioned space12for sensing a level of pathogens in the conditioned space12, and more particularly, the level of airborne pathogens in the conditioned space12. Pathogens include, but are not limited to, bacteria, viruses, mold and fungi. The pathogen sensor42is preferably an electrochemical sensor chip for rapid pathogen detection and generation of an electrical signal indicative of a level of pathogens sensed. Several rapid response pathogen sensing technologies currently exist and are suitable for use with the present invention. In other constructions, other types of pathogen sensors may be employed.

The pathogen sensor42is operatively coupled to a controller46for supplying an electrical signal to the controller46indicative of the level of pathogens in the conditioned space12. The controller46is operatively coupled to the variable speed fan30for controlling the speed of the fan30dependent on the level of pathogens sensed by the pathogen sensor42. The controller46is operable to decrease the speed of the variable speed fan30in response to an increase in the level of airborne pathogens sensed by the pathogen sensor42. Conversely, the controller46is operable to increase the speed of the variable speed fan30in response to a decrease in the level of airborne pathogens sensed by the pathogen sensor42. Decreasing the speed of the variable speed fan30increases a dwell time of a volume of air within the reaction chamber14. Conversely, increasing the speed of the variable speed fan30decreases the dwell time of a volume of air within the reaction chamber14.

The generation of ROS decreases when the fan30is slowed because less oxygen is introduced to the generator26for conversion into ROS. However, the short-lived ROS, which are active substantially within the reaction chamber14, are able to find and neutralize more pathogens when pathogens dwell longer within the reaction chamber14. Thus, when the fan speed is decreased, more airborne pathogens are neutralized within the reaction chamber14. Conversely, the generation of ROS increases when the speed of the fan30is increased because more oxygen is converted to ROS. When the fan speed is increased, more long-lived ROS are released to the conditioned space12for increased surface sanitization in the conditioned space. Thus, maximum benefit of the air sanitization system10is achieved in both pathogen removal from the room atmosphere (i.e., the conditioned space12) as well as surface sanitization within the conditioned space12by decreasing the fan speed with increasing pathogen level, and increasing the fan speed with decreasing pathogen level.

FIG. 2illustrates an algorithm for controlling the air sanitization system10. At action50, the algorithm starts and moves to action54. At action54, the controller46sets the speed of the fan30to 100% (full speed), and moves to action58. At action58, the controller46reads a signal from the pathogen sensor42corresponding to a pathogen level, and moves to action62. At action62, the controller46determines whether the pathogen level is greater than or equal to a maximum pathogen level, which is a predetermined level at which more pathogen removal within the reaction chamber14is desired. If the pathogen level is greater than or equal to the maximum, the controller46moves to action66to determine whether the speed of the fan30is equal to twenty percent. If the speed is not equal to twenty percent, the controller46moves to action70and decreases the fan speed by five percent, and then moves to action74to a ten minute delay before returning to action58. If the speed is equal to twenty percent, the controller46moves directly to action74for a ten minute delay before returning to action58.

If, at action62, the pathogen level is not greater than or equal to the maximum, the controller moves to action78to determine whether the fan speed is equal to 100% (full speed). If the fan speed is not equal to 100%, the controller moves to action82to determine whether the pathogen level is less than or equal to a minimum pathogen level, which is a predetermined level at which more surface sanitization is desired. If the pathogen level is less than or equal to the minimum, the controller46moves to action86to increase the speed of the fan30by five percent, and then moves to action74to a ten minute delay before returning to action58. If the pathogen level is not less than nor equal to the minimum, the controller46moves to action74for a ten minute delay before returning to action58.

In operation, the ROS generator26generates short- and long-lived ROS for cleaning the air and surfaces of the conditioned space12. The controller46decreases the speed of the fan30in five percent increments when the pathogen level is over the maximum pathogen level, but does not decrease the speed below twenty percent. Decreasing the fan speed increases the dwell time of the pathogen-containing air in the reaction chamber14, which increases the effectiveness of the short-lived ROS. If the pathogen level is below the minimum level, the controller46increases the speed of the fan30in five percent increments. At higher fan speeds, more long-lived ROS are delivered to the conditioned space12for surface and air sanitization. Regardless of the fan speed, cleaned air and ROS are delivered from the reaction chamber14to the conditioned space12by way of the diffuser34, which distributes the air and ROS throughout the conditioned space.

In another construction, the controller46includes a user input feature. For example, a user may select one of maximum air sanitization and maximum surface decontamination. When maximum air sanitization is selected, the controller46decreases the fan speed. For example, the fan speed may be decreased to twenty percent. When maximum surface decontamination is selected, the controller46increases the fan speed. For example, the fan speed may be increased to full speed. The user input feature may be added to the air sanitization system10ofFIGS. 1-2, or may be a feature of a different air sanitization system.

Thus, the invention provides, among other things, a control system for an air sanitization system and a method of operating the air sanitization system. Various features and advantages of the invention are set forth in the following claims.