Abstract: A filter box for a surface maintenance machine incorporating aspects of a fan housing. In one example, a filter box for a sweeping machine is provided with an impeller fan housing beneath a cylindrical filter. Operation of the impeller fan draws air from a debris hopper, through the cylindrical filter, and through an expansion chamber defined by a scroll conduit prior to outlet to atmosphere.

Abstract: An air cleaner having a manipulator is disclosed. The manipulator (200) includes a rotary manipulation unit (300), which is provided so as to be movable between a first position, at which the rotary manipulation unit is retracted into the air cleaner, and a second position, to which the rotary manipulation unit is extracted from the air cleaner to enable a user to manipulate the rotary manipulation unit. The manipulator further includes a lift unit (400), which is installed in the air cleaner to move the rotary manipulation unit between the first position and the second position. In the present invention, the manipulator can control several functions of the air cleaner obviating the need for having several control buttons, thus being more convenient for a user. Furthermore, the present invention can prevent water from permeating a PCB mounted in the rotary manipulation unit, thus preventing malfunction of the encoder unit.

Abstract: An objective of the invention is to obtain a cleaning unit which allows a cleaning mechanism, such as a dust removal device, for an air filter to be easily mounted in an indoor unit of an air conditioner that has an air filter on the intake side of an indoor fan. The cleaning unit includes: a chamber casing (101) connected to a room side of an indoor main unit (10) having an indoor heat exchanger (22) and an indoor fan (21) which draws air from the room and blows the air to the indoor heat exchanger (22); an air filter (30) provided in the chamber casing (101) on an intake side of the indoor fan (21); and a dust removal device (50) configured to remove dust captured by the air filter (30).

Abstract: In an indoor unit of an air conditioner including an air filter arranged on a suction side of an indoor fan, dust trapped on the air filter is reliably and efficiently removed by a simple structure. For that purpose, an indoor unit (13) is provided with a dust remover (50) for removing dust trapped on an air filter (40) arranged on a suction side of an indoor fan (39), and a filter presser (70) for pressing a frame (42) of the air filter (40) so as to press the air filter (40) against the dust remover (50). The air filter (40) is configured to move relative to the dust remover (50), and the filter presser (70).

Abstract: Aseptic bottling or container filling plant with a clean room arrangement enclosing the aseptic bottling or container filling plant and a filter unit for filtering air entering the clean room, and a method of operation thereof.

Abstract: A portable air filter having a cylindrical, perforated shell with an end wall at one end closing the shell and an end wall at the other end having an opening. A hepa filter is removably mounted within the shell adjacent the perforations. The air filter has a blower unit with a through duct and a fan and a motor in the duct. The blower unit is detachably mountable on the shell adjacent the end wall at the other end with one open end of the duct extending through the opening in the end wall. Air is drawn through the perforated shell and hepa filter into the duct and out of the duct through its other open end away from the air filter.

Abstract: Enclosures for use in hazardous areas include sintered filters for thermal management. The enclosures include an opening to which a filter holder housing and sintered filter are coupled. The enclosures can also include a second opening to which a vent or a second filter holder housing and sintered filter are coupled. The internal temperature of the enclosures can be actively managed by such a system because air within the enclosure can be displaced to and from the atmosphere through the sintered filters. Air from the atmosphere enters the enclosure via the second opening and exits the enclosure via the first opening.

Abstract: A dust collection system has a cyclone separator in which dust is separated from an air stream and the air stream is passed from a separator and flows through a final filter back into the ambient air. A flame arrester is positioned downstream of the separator, either in advance of or after the final filter. The flame arrester defines a multiplicity of narrow channels to permit exhaust air flow but block any flame front. In a preferred embodiment the flame arrester is in the form of a sheath of a porous metal material surrounding the final filter. The sheath may comprise a metal wire mesh screen, with a guard cage surrounding the screen.

Abstract: A dust collection arrangement employs a variable frequency drive to supply AC to its fan motor. A current sensor measures the current drawn by the motor, and this is compared with a preset value. The variable frequency drive adjusts the frequency of the AC applied to the motor to maintain the motor current at the preset level. This keeps the flow of air in the system optimal as dust producing tools are added or taken off.

Abstract: A dust collector arrangement has a dust separator supported on a frame, with a lid for the dust collection barrel is mounted onto the frame below it. The lid is supported at a fixed elevation above the surface of the shop floor to create a space or clearance between the rim of the dust collection barrel and the lid. The barrel is supported on casters, and can be rolled into place under the rim, and can be rolled out for emptying. Over-center latches positioned at intervals around the upper part of the barrel side wall, engage corresponding structure on the lid. These pull the barrel upwards against the lid and with the barrel casters lifted off the floor surface. The latch members release to lower the barrel for emptying.

Abstract: A filter element including an end cap is provided. The end cap includes an annular seal support carrying an annular seal member and a mounting arrangement to seal and support the filter element in a filter housing. The end cap is configure to engage with a mating engagement structure of the housing to provide self alignment feature of the filter element.

Abstract: A system for separating contaminants from an airstream, including a centrifugal fan and housing; a contaminant containment vessel mounted to an outer surface of the housing; and a diverter in the airstream downstream of the fan and within the housing, the diverter being configured to separate a portion of the airstream from a remainder of the airstream, accelerate the portion of the airstream towards the containment vessel, and thereafter guide the portion of the airstream towards the remainder of the airstream. The diverter preferably does not negatively impact the rated performance of the fan, such that a performance of the system is not measurably different than the rated performance of the fan and housing combination. The diverter may accelerate contaminants entrained in the airstream toward the containment vessel, thereby separating the contaminants from the airstream.

Abstract: A dust collector includes a housing and a case. The housing forms therein an air chamber in which filter cylinders are mounted. The case has an interior space divided by a separation board into an air inlet compartment communicating the air chamber of the housing and an air outlet compartment communicating the air inlet compartment. A blower unit is mounted to the separation board and includes blast box mounted to the separation board in the air inlet compartment and a motor arranged in the air outlet compartment in such a way that an output spindle of the motor extending into the blast box and carrying a blade assembly. With such an arrangement, resonance caused by wind shear sound of the blade assembly is eliminated. Heat generated by the operation of the motor can be removed by air flow passing through the air outlet compartment to realize cooling of the motor.

Abstract: A particle separating structure for use with a turbine engine. The particle separating structure includes a main housing, first swirling structure, and second swirling structure. The first swirling structure is provided for swirling cooling fluid passing through a first cooling fluid flowpath defined in the main housing. The second swirling structure is provided for swirling cooling fluid passing through a second cooling fluid flowpath defined in the main housing. The first swirling structure is positionable in at least two positions, a first position allowing cooling fluid to pass through the first cooling fluid flowpath and a second position allowing cooling fluid to pass through the first and second cooling fluid flowpaths. The swirling of the cooling fluid causes particles in the cooling fluid to pass to a particle discharge zone while the cooling fluid passes out of the main housing through a cooling fluid outlet.

Abstract: A foldable dust collector of the present invention includes a supporting portion, a case and an air pump. The supporting portion is foldable. The case is disposed on the supporting portion. The case is pivotable with respect to the supporting portion. The air pump is disposed on the case. The air pump is used for drawing air into the case. Therefore, the foldable dust collector of the present invention can be transformed. A width of the foldable dust collector is changeable. As such, the foldable dust collector is easier to be stored or be transported. Moreover, the foldable dust collector can be used in a small space.

Abstract: An indoor unit of an air conditioner includes: a casing (10); an indoor fan (21); an air filter (30); an inlet port (24) in which the air filter (30) is attached, and a divider plate (25) for dividing space in the casing (10) into a room upstream of air passing through the air filter (30) and a room downstream of air passing through the air filter (30). The indoor unit conditions room air sucked into the casing (0) through the air filter (30). The indoor unit includes a rotating brush (51) for removing dust trapped on the air filter (30), and a dust container (90) for containing the removed dust. An access opening (70) which allows for checking of an electrical component box (72) in the casing (10) is formed in the divider plate (25), and an access lid (71) for closing the access opening (70) is provided.

Abstract: The present invention provides an air filter including a main body, a pressure fan, a filter mode and a fixing assembly. The main body has a containing room, an entrance hole and an exit hole. The pressure fan is disposed in the containing room. The filter mode includes a first filter layer, a second filter layer and a frame body. The first filter layer is disposed in the entrance hole, and the second filter layer is disposed in the frame body. As such, users can select to use only the first filter layer or both filter layers at one time. Moreover, users only need to let the frame body pivot to a position away from the entrance hole so that users can change the filter layers faster and easier.

Abstract: An air filtration system includes a housing that is interchangeably positioned within a plenum that is in fluid communication between the housing and a room. A fan is positioned within the housing and configured to draw contaminated air from the plenum. At least one filter member is positioned within the housing and configured to filter the contaminated air. A flexible duct is configured to channel filtered air from the housing to the room. The flexible duct is configured to enable the interchangeability of the housing.

Abstract: A protective device is provided for an air filter that is substantially cylindrical and is intended to equip in particular a generating set. The filter is intended to be press fitted to a duct of said set. The protective device includes at least two portions that are securable radially on the filter in order to form a protective case surrounding the filter.

Abstract: A dust-sucking and air-cleaning composite structure is provided with a dust-sucking body and an air-cleaning body. The top surface of the air-cleaning body is provided with a vertically opening cavity. The cavity is recessed downward toward the interior of the air-cleaning body and has an opening facing upwardly. The inner profile of the cavity corresponds to the outer profile of the dust-sucking body, thereby allowing the dust-sucking body to be movably inserted into the cavity to be electrically coupled to the air-cleaning body.

Abstract: The present invention relates to a cooling system. More particularly, the present invention relates to a cooling system for removing dust from air being drawn for cooling heat generation components of an electronic product, for improving convenience in maintenance or repair of the electronic product.

Abstract: A dust collector includes a housing provided with a suction port and a discharge port, a motor-driven fan located in a fan chamber in the housing, an air suction chamber located between the suction port and the fan chamber, a main filter located in the air suction chamber, a drum member that is so located in the fan chamber as to enclose the fan, and a drum filter mounted around an outer circumferential plane of the drum member. The main filter is comprised of a box-shaped filter case that is ejectable from the air suction chamber and two or more filter elements that are set in the filter case in layers, and the filter elements are selected from a plurality of filters which have the same or different performances.

Abstract: A cyclonic dust collector arrangement employs a cyclone that has a conic body formed of a conic wall. An upper divider plate closes off the upper end of the conic body, with a vortex tube descending from a central passage in the divider plate. The conic body has a narrow nose at a lower end so that the upper divider plate and the lower nose define a cyclonic chamber within the conic body. The inlet conduit penetrates the conic wall below the divider plate. The fan chamber of the separator is mounted above the divider plate, and serves to induce air flow from the inlet conduit into the cyclonic chamber, and through said vortex tube into the fan chamber. The air is discharged through a final filter. This construction has reduced manufacture costs and improved dust separation.

Abstract: A high cleaning efficiency room air cleaner with a slim profile providing a clean air delivery rate sufficient to clean any ordinary size room includes a flat-panel housing having an internal chamber sized to receive conventional large area flat-panel furnace filters of standard size and a fan array preferably of high efficiency, low power axial computer fans mounted to the flat-panel housing. The room air cleaner may include a scent cartridge and a UV lamp assembly.

Abstract: The present invention provides an air filter including a main body, a pressure fan, a filter mode and a fixing assembly. The main body has a containing room, an entrance hole and an exit hole. The pressure fan is disposed in the containing room. The filter mode comprises a first filter layer, a second filter layer and a frame body. The first filter layer is disposed in the entrance hole, and the second filter layer is disposed in the frame body. As such, users can select to use only the first filter layer or both filter layers at one time. Moreover, users only need to let the frame body pivot to a position away from the entrance hole so that users can change the filter layers faster and easier.

Abstract: The present invention relates to a system and method for the separation of gaseous components from gaseous mixtures in order to control emissions and treatment of the gaseous components. In one embodiment, the system makes use of a fan or gas moving device to first impose centrifugal forces on gas streams as the gas moves from the center of the fan toward the periphery of the fan housing. Heavier gases are forced to the outer regions of the fan housing while lighter gases remain closer to the fan axis. The heavier gases and lighter gases exiting the fan housing flow into a duct at different flow rates, and the heavier gases are diverted from the larger volume gas streams and then processed.

Abstract: A filter frame is removably attachable to a box fan. The filter frame is adapted for receiving a standard HVAC-style filter for removing contaminants from air flow induced by the fan. In this manner, a cost-effective means for filtering a flow of air is provided for residential and commercial settings. The filter frame is adaptable to a variety of standard box fan types of different styles and dimensions. The frame is configured to accommodate standard filters, such as those readily available from retail hardware stores and home centers.

Abstract: Dust collection structure for collecting the dust removed from an air filter of an indoor unit has been devised to reduce user's labor in collecting the dust as much as possible. An indoor unit includes, in a casing, an indoor heat exchanger, an indoor fan for sucking air from inside of a room, and blowing the air to the inside of the room, and an air filter arranged on an inlet side of the indoor fan. The dust trapped on the air filter is removed by the dust removing means, and is contained in the dust containing part. A nozzle connector for arranging a nozzle of a cleaner at a predetermined position where suction of the contained dust is allowed is provided at a downstream outlet of a dust collection path as a transfer path for transferring the dust in collecting the contained dust.

Abstract: A deodorizing device is provided featuring a collection mouthpiece having an intake port and an internal channel, and a pump unit attachable to the collection mouthpiece and operable to draw malodorous air into the intake port and through the internal channel when the collection mouthpiece is attached to the pump unit. Also provided are a pump unit, a filter cartridge, a mount, and methods of assembling and using the same.

Abstract: The present invention relates to a method and a system for treating polluted gases prior to their emission into the atmosphere. The system comprises a treatment chamber having an inlet for receiving polluted gas and an outlet for expelling treated gas, the treatment chamber including at least one treatment cell having a filtering layer for treating the polluted gas when the polluted gas comes in contact with the filtering layer. The system also contains a powder container connected to the treatment chamber such that air laden with the powder can flow to the treatment chamber to form a filtering layer on the at least one treatment cell. The system contains an air flow generator connected to the outlet of the treatment chamber and to the container which is connected to the treatment chamber, for causing air flow to the container, to the treatment chamber and in the environment.

Abstract: A ventilation device uses a cross-flow fan and one or more filters, where the filter preferably has a J-shape that at least partially surrounds the rotor of the cross-flow fan. In one embodiment, the filter includes a plurality of pleats, preferably along a bottom surface of the filter. The filters preferably remove particles, undesired gases, and micro-organisms. A filtration and ventilation system with at least one first ventilation device and at least one second ventilation device larger than the first ventilation device, as well as a method of filtering contaminants out of air using a personal ventilation device, are also disclosed.

Abstract: A device is provided that is capable of circulating air throughout a personal space as well as collecting and preventing the build up of dust and other particulate matter by drawing in air from the surrounding environment and removing some dust, allergens and other such particulate matter therefrom. The filtered air is then expelled out of the device and back into the surrounding environment. The device includes a housing defining an interior space having a motor and fan assembly disposed therein. The housing includes an inlet with a filter provided therein such that air drawn in through the inlet is filtered. The air is then expelled through a circumferentially disposed outlet. The filter element preferably includes a lock and key system configured to prevent operation of the device in the absence of a properly keyed filter.

Abstract: An air filter assembly has a fan, pre-filter, a main filter, and a control circuit which generates various signals to the user as to when the pre-filter and the main filter should be replaced. The control circuit detects when the pre-filter should be replaced from two conditions: a first pre-filter replacement condition based decreased air flow, and a second pre-filter replacement condition based on cumulative operating time. The control circuit detects when the main filter should be replaced based on a formula containing a number of the occurrences of the first pre-filter replacement condition and a number of occurrences of the second pre-filter replacement condition. The control circuit also detects a main filter replacement condition based on cumulative operating time of main filter. The main filter can have a fuse that is blown when the main filter should be replaced.

Abstract: Disclosed is an installation structure for a dustproof net to be arranged in a machine, which has an engine, a cooling fan for producing cooling air to cool the engine, plural heat exchangers arranged on an upstream side of the cooling fan, and a compartment with the engine, cooling fan and plural heat exchangers accommodated therein, such that the dustproof net is arranged at a position on a side upstream of the heat exchanger located most upstream among the plural heat exchanger relative to a flow of air drawn in by the cooling fan and in isolation from the most upstream heat exchanger to remove dust contained in the air drawn in by the cooling fan. The dustproof net is provided with a support structure for supporting the dustproof net on members that form the compartment.

Abstract: A low depth telescoping downdraft ventilator controlled by an electronic controller providing a precisely controlled and efficient way of removing gases and fumes is disclosed. The low depth telescoping downdraft ventilator has the ability to fit behind a built-in oven placed below a cook top unit. The telescoping downdraft ventilator has an almost infinitely selectable range of heights above a cook top with a built in oven. The ventilator collects and draws in exhaust fumes and smoke, filters it and re-circulates or expels it either outdoors or indoors. The inner member of the telescoping ventilator may house the exhaust fans and may move up or down without the use of mechanical switches for elevation detection and stopping. The ventilator may have sensors to detect temperatures, filter change need, fan speeds, telescoping stop points, energy consumption, resistance and voltage, enabling programmable set point operation.

Abstract: A grow light cooling and grow room odor pollution control system that includes an air plenum with a plurality of air inlets; a plurality of air ducts connecting each air inlet to at least one grow light housing, at least one air outlet; an air pump mounted in the air plenum, and at least one filter operatively coupled to the air pump and disposed between all of the air inlets and the air outlet, such that the air pump pulls hot and odorous air from nearby grow light housings into the air plenum through the air inlets, through the air filter, and then out from the plenum for dissipation in the outside atmosphere or for use in heating a structure.

Abstract: An apparatus for purifying and humidifying air which enables separate supply of purified air and humidified air and controls the amount of humidified air discharged and which includes dual flow paths to increase the efficiency of air transfer. The apparatus includes a case having a suction port through which external air is introduced thereinto and a discharge port through which the introduced air is discharged, a circulation fan for causing the introduced air to flow toward the discharge port, a filter unit disposed in the case to filter the introduced air, a humidification unit disposed at a low position in the case to supply the air passed through the filter unit with moisture, and a flow path control unit disposed between the suction port and the humidification unit to control flow of the air passed through the filter unit.

Abstract: Various embodiments of air treatment devices (and housings therefor) are provided. The housings are generally configured to provide air treatment devices that lessen the perceived size of the air treatment devices. Further, embodiments provide housings that are typically easier to clean and maintain and to provide ease in access to internal components of the air treatment devices. Embodiments may also position a control display associated with an air treatment device, such that the control display is visible from a position in front and above the air treatment device. Embodiments may also be configured to minimize and/or inhibit air exiting from the air outlet of the air treatment device from immediately reentering the air inlet and thus being recirculated.

Abstract: A utility vacuum that may be configured to employ a disposable bag or removable and reusable container for the collection of dirt and debris that are drawn into the utility vacuum. The utility vacuum may employ one or more movable legs that are movable between an extended position, which provides relatively stable operation of the utility vacuum, and a retracted position, which reduces the footprint of the utility vacuum so that it is easier to store.

Abstract: A grease containment apparatus to remove grease and other contaminants from hot air exiting a kitchen area through a vent system which includes a vertical separator.

Abstract: A dust bin for a robotic vacuum comprises a dust bin frame having a cavity defined therein to receive debris, a filter frame disposed within the dust bin frame and defining two filter openings at opposite sides thereof, and a central impeller disposed adjacent to or under the filter frame to draw air from outside of the dust bin into the dust bin. The dust bin also comprises two air filters, one air filter being located on each side of the central impeller, each air filter being inserted into one of the filter openings, each filter having an overhang around a perimeter thereof that includes a sealing face to form a vacuum-assisted seal with the filter frame when air is drawn into the dust bin.

Abstract: A sealed air purifier is disclosed. A housing is formed by connecting a first shell and a second shell. The first shell and the second shell communicate via separable connecting base and connector. A retractable bag encloses the connecting base and the connector. A sealing structure is provided between both ends of the bag. The first shell has an air inlet connecting the inside and the outside and a gate to control the airflow. A compression assembly is disposed in the first shell. The second shell has an air outlet connecting the inside and the outside and a blocking element to control the air outlet. The second shell has a sterilizing device and a super ULPA filter. When the gate closes the air inlet, the compression assembly, sterilizing device, and the air outlet close correspondingly, so that the inside of the housing is isolated. Thus, the viruses remaining therein do not spread with air.

Abstract: An air filter having an inlet for air and an outlet for air comprises a body having a central channel, a first side with a first area, a second side having a second area, and a middle having a middle area, positioned between the first side and the second side. The middle area is less than the first area and less than the second area. A first fan is positioned in the body near the first side, and a second fan positioned in the body near the second side, and each fan blows air in the same direction. A filter cartridge is positioned in the central channel at the middle, wherein during operation air flows from the inlet to the filter cartridge to the outlet.

Abstract: A powered air cleaning system has a flow path extending through the system from an inlet to an outlet. A motor-driven fan is located along the flow path to draw particulate debris laden air into the inlet and rotate it about an axis to form a rotating flow that stratifies the debris laden air with the heaviest particles in the outermost orbits of the rotating flow. An ejector port ejects particulate debris laden air from the stratified rotating flow in the system. At least one de-swirl component located within the rotating flow aerodynamically redirects clean air from the innermost orbits of the stratified rotating flow toward the outlet to provide a positive airflow pressure out of the outlet. The system has a variable speed fan motor and an integrated controller for adjusting the speed of the motor and thereby the flow rate of clean air through the outlet of the system. The controller receives a signal that is a function of airflow requirements of a device supplied with clean air by the system.

Abstract: Ejector devices and systems are provided, that entrain ambient air within a primary stream of pressurized air, for use in a variety of applications including aircraft, buildings and other stationary structures. The ejector draws ambient air through an air treatment means such as a filter before its entrainment within the primary stream. The combined streams are then delivered to a ventilation system, an air curtain or other suitable recipient of treated, thermally conditioned air. The systems include diffusers, air curtain systems and variable air volume ventilation systems for aircraft and other vehicles.

Abstract: Apparatus for evacuating water and dirt from a cooler box of a cooling system, incorporated with a blow-off for an air screen of the system. The water and dirt will flow through an aperture in a lower region of the cooler box into a smaller box of the apparatus disposed therebelow. A fan operable for generating the air flow through the air screen and the cooler box, also blows a portion of the flow through a blow-off channel to the air screen for blowing debris away from the air screen. The channel and smaller box are cooperatively configured such that the air flow through the channel will generate a partial vacuum condition in the smaller box operable for evacuating the water and the dirt into the channel so as to be carried away with debris from the air screen.

Abstract: A room air purifier is provided is provided that has a housing that defines a floor supply duct inlet, a room air inlet, and an outlet. An air mixing chamber within the housing is in direct communication with said room air inlet and said floor supply duct inlet. A filter is disposed in the housing. A fan is disposed in said housing between the outlet of the filter and the outlet side of the filter. An air channel panel is disposed in a filter inlet area between the air mixing chamber and the filter. Various sensors may be deployed to control temperature, and to prevent unpurified air from exiting the room air purifier. Optionally, an additional wall supply inlet may be placed in fluid communication with the air mixing chamber to provide a second extra-room source of air.

Abstract: The window filter apparatus provides a framework for holding filters within the frame of windows, thereby offering filtered outside air for a building, without having to run an air conditioner. The apparatus further provides for filtering noise and light by the same filters. Box fans are ideal companions for the apparatus for drawing additional outside air into a building. No additional hardware or tools are needed. There is no invasion of windows or window frames.

Abstract: An apparatus for purifying and humidifying air which enables separate supply of purified air and humidified air and controls the amount of humidified air discharged and which includes dual flow paths to increase the efficiency of air transfer. The apparatus includes a case having a suction port through which external air is introduced thereinto and a discharge port through which the introduced air is discharged, a circulation fan for causing the introduced air to flow toward the discharge port, a filter unit disposed in the case to filter the introduced air, a humidification unit disposed at a low position in the case to supply the air passed through the filter unit with moisture, and a flow path control unit disposed between the suction port and the humidification unit to control flow of the air passed through the filter unit.

Abstract: A housing for a centrifugal fan includes a surrounding wall extending upwardly from a periphery of a bottom wall with an air inlet, and including a surrounding wall body defining an opening, a protruding wall body extending outwardly from the surrounding wall body, corresponding to the opening, and having a dust-discharging hole, and a shielding plate disposed on the protruding wall body. The surrounding wall body and the bottom wall cooperatively define an accommodation space communicated with the air inlet, and an air outlet communicated with the accommodation space. The protruding wall body, the shielding plate, and the bottom wall cooperatively define a turbulence space communicated with the accommodation space. The shielding plate is movable between a closed position to close the dust-discharging hole, and an open position to open the dust-discharging hole so as to permit fluid communication between the turbulence space and the outside environment.