Patent Publication Number: US-2017358189-A1

Title: Smoke detector chamber

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This patent application is a continuation of U.S. patent application Ser. No. 14/921,307 filed on Oct. 23, 2015, which is a continuation of U.S. patent application Ser. No. 14/713,770 filed on May 15, 2015, now U.S. Pat. No. 9,196,141. Priority to these patent applications is claimed and these patent applications are hereby incorporated by reference for all purposes. 
    
    
     BACKGROUND 
     In some forms of smoke detectors, such as optical smoke detectors, a smoke chamber is used. A smoke chamber is used for creating a controlled environment in which electromagnetic radiation is emitted and sensed. While it may be desired to maximize airflow between the interior of the smoke chamber and an exterior environment, the smoke chamber may need to be designed in such a way as to limit stray electromagnetic radiation from entering the interior of the smoke chamber from an exterior environment. 
     SUMMARY 
     In some embodiments, a smoke chamber for a smoke detector is presented. The smoke chamber may include a housing, having a first portion and a second portion. The first portion may be through which an electromagnetic sensor and two or more electromagnetic emitters interact with an airspace within the housing. The second portion may have an airflow surface that at least partially defines a curved airflow path between the airspace within the housing and an external environment. The curved airflow path may curve radially outward. The smoke chamber may include a plurality of radially-aligned airflow fins located on the airflow surface. 
     Embodiments of such a smoke chamber may include one or more of the following features: The smoke chamber may include a plurality of steps disposed on the airflow surface such that the curved path that curves radially outward is defined by the plurality of steps. The smoke chamber may include a plurality of actuatable clips, wherein the first portion and the second portion of the housing are two pieces that are coupled together by the plurality of actuatable clips. The smoke chamber may include a rotational alignment extrusion positioned to cause the two pieces of the housing to rotationally align when coupled together by the plurality of actuatable clips. The first portion may include a plurality of crush ribs, the plurality of crush ribs for holding the electromagnetic sensor and the one or more electromagnetic emitters in position for interacting with the airspace within the housing. The first portion of the housing may define a plurality of anchor bays for the electromagnetic sensor and the two or more electromagnetic emitters such that electromagnetic radiation that was generated by the one or more electromagnetic emitters and was deflected by a smoke particle is sensed by the electromagnetic sensor via forward scattering. The first side of the housing may define anchor bays for at least two electromagnetic emitters. The smoke chamber may include cylindrical mesh that encircles the housing and filters airflow between the airspace within the housing and the external environment. The smoke chamber may include a conductive cap and a conductive base, wherein the cylindrical mesh is conductive such that the housing is encased by a Faraday shield. The anchor bays for the one or more electromagnetic emitters and the electromagnetic sensor are offset from parallel by an angle of between 35 degrees and 45 degrees. The first portion of the housing includes a dust collector disposed at the center point of the first portion, the dust collector comprises a plurality of walls and a depressed floor within the first portion of the housing. In some embodiments, majority of an interior surface of the first side of the housing is polished. The housing may include a second airflow surface that defines the curved airflow path in conjunction with the airflow surface, and the second airflow surface in combination with the airflow surface prevents line-of-sight access to the airspace within the housing. The curved airflow path between the airflow surface and the second airflow surface may be at least 3 millimeters. Each anchor bay of the plurality of anchor bays may each define a rectangular aperture. A circular interior wall of the housing may be covered in a plurality of ribs. The housing may include a second side that has, on an interior surface, a plurality of pyramidal extrusions. 
     In some embodiments, a smoke detector is presented. The smoke detector may include a plurality of electromagnetic emitters. The smoke detector may include an electromagnetic sensor. The smoke detector may include a smoke chamber. The smoke chamber may include a housing, through which the electromagnetic sensor and the electromagnetic emitter interact with an airspace within the housing. The housing may include an airflow surface that at least partially defines an airflow path between the airspace within the housing and an external environment, the airflow surface defining a curved airflow path that curves radially outward. The housing may include a plurality of radially-aligned airflow fins located on the airflow surface around the airspace. The one or more electromagnetic emitters may include a plurality of electromagnetic emitters, comprising an infrared light emitting diode and a light emitting diode that emits blue light. 
     In some embodiments, a smoke chamber apparatus for a smoke detector is presented. The apparatus may include a housing means, through which an electromagnetic sensing means and an electromagnetic emitter means interact with an airspace within the housing means. The housing means may include an airflow means that at least partially defines an airflow path between the airspace within the housing means and an external environment, the airflow means defining a curved airflow path that curves radially outward. The housing means may also include a plurality of radially-aligned airflow means configured to direct air toward a center of the airspace. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further understanding of the nature and advantages of various embodiments may be realized by reference to the following figures. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. 
         FIGS. 1A and 1B  illustrate an embodiment of a smart combined smoke detector and carbon monoxide device. 
         FIGS. 2A, 2B, 2C, and 2D  illustrate an embodiment of an exploded smart combined smoke detector and carbon monoxide device. 
         FIG. 3  illustrates an embodiment of a smoke chamber. 
         FIG. 4  illustrates an embodiment of the smoke chamber of  FIG. 3  separated into constituent parts. 
         FIGS. 5A and 5B  illustrate a cross section of an embodiment of the smoke chamber of  FIG. 3 . 
         FIG. 6  illustrates an angular projection of an embodiment of a top component of the smoke chamber. 
         FIG. 7  illustrates a bottom view of an embodiment of a top component of the smoke chamber. 
         FIG. 8  illustrates an angular projection of an embodiment of the bottom component of the smoke chamber. 
         FIG. 9  illustrates a top view of an embodiment of the bottom component of the smoke chamber. 
         FIG. 10  illustrates a side view of an embodiment of the bottom component of the smoke chamber. 
         FIG. 11  illustrates another angular projection of an embodiment of the bottom component of the smoke chamber. 
         FIGS. 12A-12C  illustrate an embodiment of a mesh that can be wrapped around the various detailed embodiments of smoke chambers to help filter large particulate matter. 
         FIG. 13  illustrates an embodiment of a method for using two modes for monitoring for smoke in a smoke chamber. 
         FIG. 14  illustrates an embodiment of a method for using three modes for monitoring for smoke in a smoke chamber. 
         FIG. 15  illustrates an embodiment of a method for performing a mode for detecting smoke within a smoke chamber. 
         FIG. 16  illustrates an embodiment of a method for performing another mode for detecting smoke within a smoke chamber. 
         FIG. 17  illustrates an embodiment of a system that may perform various methods of detecting smoke. 
         FIG. 18  illustrates an embodiment of a graph showing the relationship between infrared and blue light measurements by an EM sensor. 
         FIG. 19  illustrates an embodiment of the graph of  FIG. 18  showing data points from two foam block fires. 
         FIG. 20  illustrates an embodiment of the graph of  FIG. 19  showing data points from the two foam block fires in three dimensions against time. 
         FIG. 21  illustrates an embodiment of a computer system which may be incorporated as part of the smoke detector and/or carbon monoxide devices detailed herein. 
     
    
    
     DETAILED DESCRIPTION 
     A smoke chamber that allows for increased airflow can improve the performance of an optical smoke detector. By increasing airflow and, possibly, channeling air to a center of the smoke chamber, the speed at which the smoke is detected may be increased. Further, by using multiple wavelengths of electromagnetic (EM) radiation, smoke from various types of fires, such as flaming fires and smoldering fires, may be detected faster. Such a smoke chamber may be designed such that alignment between one or more EM emitters and one or more EM sensors causes the one or more EM sensors to detect EM radiation deflected by particulate smoke matter via forward scattering. 
     A smoke chamber may be ideally configured to allow no light from outside of the smoke chamber into an airspace within the housing of the smoke chamber while still allowing for air to be readily exchanged between the airspace within the housing of the smoke chamber and the exterior environment (e.g., outside of the smoke chamber, such as the room in which the smoke detector is installed). The smoke chamber may include multiple parts, such as a top component and a bottom component that are manufactured separated and are coupled together to form the smoke chamber. The smoke chamber may have a circular cross-section and may have a surface that generally curves radially outward from a center axis of the smoke chamber. This surface may have a series of “steps” which are perpendicular protrusions on the curved surface that help prevent light from being reflected by the surface from the exterior environment into the smoke chamber. Along the radially curved surface, a series of airflow fins that are radially aligned with a center axis of the smoke chamber may be positioned. These airflow fins may serve to direct airflow towards the center of the smoke chamber, which can help smoke be detected quickly. 
     By increasing the airflow between the airspace and the exterior environment, it may be possible to wrap the air exchange portion of the smoke chamber with a mesh while still maintaining sufficient airflow to meet all relevant legal requirements and detect smoke from various types of fires in a timely fashion. A mesh may be wrapped around the smoke chamber to limit entry of undesired matter (e.g., dust, bugs) into the smoke chamber while still allowing smoke particulate matter entry. The mesh may be metallic and, along with a metallic cap and metallic base, may serve as a metallic shield (a Faraday cage or Faraday shield) that encompasses the smoke chamber, which decreases EM noise that can affect the one or more EM sensors. 
     Various embodiments of smoke chambers, including the above aspects and aspects yet to be noted, are described in detail in relation to the figures that follow. For overall understanding, a big picture view of a device that uses such a smoke chamber is first described. Such a device may be a dedicated smoke detector or a combination device, such as carbon-monoxide detector and smoke detector.  FIG. 1A  illustrates an embodiment of a smart combined smoke detector and carbon monoxide device  100 A. Such an embodiment of a smart combined smoke detector and carbon monoxide device  100 A may be suitable for mounting to a wall or ceiling in a room (or other location) within a structure in which smoke and/or carbon monoxide is to be monitored. Device  100 A may be “smart,” meaning the device  100 A can communicate, likely wirelessly, with one or more other devices or networks. For instance, device  100 A may communicate with a remote server via the Internet and, possibly, a home wireless network (e.g., an IEEE 802.11a/b/g network, 802.15 network, such as using the Zigbee® or Z-Wave® specification). Such a smart device may allow for a user to interact with the device via wireless communication, either via a direct or network connection between a computerized device (e.g., cellular phone, tablet computer, laptop computer, or desktop computer) and the smart device. 
       FIG. 1A  illustrates an angular top projection view of combined smoke detector and carbon monoxide device  100 A. Device  100 A may generally be square or rectangular and have rounded corners. Visible in the angular top projection view are various components of the combined smoke detector and carbon monoxide device  100 A, including: cover grille  110 , lens/button  120 , and enclosure  130 . Cover grille  110  may serve to allow air to enter combined smoke detector and carbon monoxide device  100 A through many holes while giving device  100 A a pleasing aesthetic appearance. Cover grille  110  may further serve to reflect light into the external environment of device  100 A from internal light sources (e.g., LEDs). Light may be routed internally to cover grille  110  by a light pipe, noted in relation to  FIGS. 2A, 2C, and 2D . It should be understood that the arrangement of holes and shape of cover grille  110  may be varied by embodiment. Lens/button  120  may serve multiple purposes. First, lens/button  120  may function as a lens, such as a Fresnel lens, for use by a sensor, such as an infrared (IR) sensor, located within device  100 A behind lens/button  120  for viewing the external environment of device  100 A. Additionally, lens/button  120  may be actuated by a user by pushing lens/button  120 . Such actuation may serve as user input to device  100 A. Enclosure  130  may serve as a housing for at least some of the components of device  100 A. 
       FIG. 1B  illustrates an angular bottom projection view of a smart combined smoke detector and carbon monoxide device  100 B. It should be understood that device  100 A and device  100 B may be the same device viewed from different angles. Visible from this view is a portion of enclosure  130 . On enclosure  130 , battery compartment door  140  is present through which a battery compartment is accessible. Also visible are airflow vents  150 - 1  and  150 - 2 , which allow air to pass through enclosure  130  and enter the smoke chamber of device  100 B. 
       FIGS. 2A, 2B, 2C, and 2D  illustrate an embodiment of an exploded smart combined smoke detector and carbon monoxide device. The devices of  FIGS. 2A-2D  can be understood as representing various views of devices  100 A and  100 B of  FIGS. 1A and 1B , respectively. In  FIG. 2A , device  200 A is shown having cover grille  110  and enclosure  130 , which together house main chassis  210 . Main chassis  210  may house various components that can be present in various embodiments of device  200 A, including speaker  220 , light pipe  230 , and microphone  240 . FIG.  2 B of an embodiment of device  200 B can be understood as illustrating the same device of  FIG. 2A , from a different viewpoint. In  FIG. 2B , cover grille  110 , enclosure  130 , airflow vent  150 - 3 , battery compartment door  140  are visible. Additionally visible is laminar flow cover  250 , which forms a shield between an underlying circuit board and enclosure  130 . Protruding through cover  250  is smoke chamber  260 . A gap may be present between enclosure  130  and laminar flow cover  250  to allow airflow through airflow vents  150  to have a relatively unobstructed path to enter and exit smoke chamber  260 . Also present in  FIG. 2B  are multiple batteries, which are installed within battery compartment  270  of device  200 B and which are accessible via battery compartment door  140 . Some or all components on main circuit board  288  may be at least partially covered by one or more laminar flow covers. Such laminar flow covers (e.g., laminar flow cover  250 ) can help laminar air flow within the device and prevent a user from inadvertently touching a component that could be sensitive to touch, such as via electro-static discharge. 
       FIG. 2C  represents a more comprehensive exploded view of a smart combined smoke detector and carbon monoxide detector device  200 C. Device  200 C may represent an alternate view of devices  100 A,  100 B,  200 A, and  200 B. Device  200 C may include: cover grille  110 , mesh  280 , lens/button  120 , light guide  281 , button flexure  283 , main chassis  210 , diaphragm  284 , passive infrared (PIR) and light emitting diode (LED) daughterboard  285 , speaker  220 , batteries  271 , carbon monoxide (CO) sensor  286 , buzzer  287 , main circuit board  288 , smoke chamber  260 , chamber shield  289 , enclosure  130 , and surface mount plate  290 . It should be understood that alternate embodiments of device  200 C may include a greater number of components or fewer components than presented in  FIG. 2C . 
     A brief description of the above-noted components that have yet to be described follows: Mesh  280  sits behind cover grille  110  to obscure external visibility of the underlying components of device  200 C while allowing for airflow through mesh  280 . Mesh  280  and grille  110  can help CO more readily enter the interior of the device, where CO sensor  286  is located. Light guide  281  serves to direct light generated by lights (e.g., LEDs such as the LEDs present on daughterboard  285 ) to the external environment of device  200 C by reflecting off of a portion of cover grille  110 . Button flexure  283  serves to allow a near-constant pressure to be placed by a user on various locations on lens/button  120  to cause actuation. Button flexure  283  may cause an actuation sensor located off-center from lens/button  120  to actuate in response to user-induced pressure on lens/button  120 . Diaphragm  284  may help isolate the PIR sensor on daughterboard  285  from dust, bugs, and other matter that may affect performance. Daughterboard  285  may have multiple lights (e.g., LEDS) and a PIR (or other form of sensor). Daughterboard  285  may be in communication with components located on main circuit board  288 . The PIR sensor or other form of sensor on daughterboard  285  may sense the external environment of device  200 C through lens/button  120 . 
     Buzzer  287 , which may be activated to make noise in case of an emergency (and when testing emergency functionality), and carbon monoxide sensor  286  may be located on main circuit board  288 . Main circuit board  288  may interface with one or more batteries  271 , which serve as either the primary source of power for the device or as a backup source of power if another source, such as power received via a wire from the grid, is unavailable. Protruding through main circuit board may be smoke chamber  260 , such that air (including smoke if present in the external environment) passing into enclosure  130  is likely to enter smoke chamber  260 . Smoke chamber  260  may be capped by chamber shield  289 , which may be conductive (e.g., metallic). Smoke chamber  260  may be encircled by a conductive (e.g., metallic) mesh (not pictured). Enclosure  130  may be attached and detached from surface mount plate  290 . Surface mount plate  290  may be configured to be attached via one or more attachment mechanism (e.g., screws or nails) to a surface, such as a wall or ceiling, to remain in a fixed position. Enclosure  130  may be attached to surface mount plate  290  and rotated to a desired orientation (e.g., for aesthetic reasons). For instance, enclosure  130  may be rotated such that a side of enclosure  130  is parallel to an edge of where a wall meets the ceiling in the room in which device  200 C is installed. 
       FIG. 2D  represents the comprehensive exploded view of the smart combined smoke detector and carbon monoxide detector device of  FIG. 2C  viewed from a reverse angle as presented in  FIG. 2C . Device  200 D may represent an alternate view of devices  100 A,  100 B,  200 A,  200 B, and  200 C. Device  200 D may include: cover grille  110 , mesh  280 , lens/button  120 , light guide  281 , button flexure  283 , main chassis  210 , diaphragm  284 , passive infrared (PIR) and light emitting diode (LED) daughterboard  285 , batteries  271 , speaker  220 , carbon monoxide (CO) sensor  286 , buzzer  287 , main circuit board  288 , smoke chamber  260 , chamber shield  289 , enclosure  130 , and surface mount plate  290 . It should be understood that alternate embodiments of device  200 D may include a greater number of components or fewer components than presented in  FIG. 2C . 
       FIG. 3  illustrates an embodiment of a smoke chamber  300 . Smoke chamber  300  can represent an embodiment of smoke chamber  260  of  FIGS. 2B and 2C . As such, it should be understood that smoke chamber  300  can be incorporated into the devices detailed in relation to  FIGS. 1A-2C  or, alternatively, could be used in some other form of device that uses a smoke chamber, such as a dedicated optical smoke detector. To be clear, an “optical smoke detector” within this document refers to any form of smoke detector that uses emitted and sensed EM radiation to sense the presence of smoke. Smoke chamber  300  is generally circular when viewed from the top or bottom, and, in three dimensions, is generally cylindrical. Similarly, the airspace within smoke chamber  300  is generally cylindrical. Such a shape can be beneficial for a smoke chamber as it decreases the regions of the airspace (e.g., elimination of corners) in which airflow can stagnate within the smoke chamber. Smoke chamber  300  can include: top component  310 , groove  320 , bottom component  350 , clips  360 , rotational alignment extrusion  370 - 1 , and rotational alignment gap  371 - 1 . Coupled with smoke chamber  300  may be EM sensor  330  and EM emitters  340  (e.g., EM emitters  340 - 1 ,  340 - 2 ). 
     Smoke chamber  300  may include two components which form the housing that creates an airspace that is substantially isolated from exterior EM radiation. Smoke chamber  300  may include top component  310  and bottom component  350  which, following manufacturing of top component  310  and bottom component  350 , are coupled together via attachment mechanisms. In some embodiments, the attachment mechanisms are clips, such as clips  360  (e.g., clips  360 - 1 ,  360 - 2 , etc.). Clips  360  may be distributed around either top component  310  or bottom component  350 . In some embodiments, four clips  360  are present; in other embodiments, fewer or greater numbers of clips  360  may be present. In the illustrated embodiment of  FIG. 3 , clips  360  are non-detachably attached to top component  310 . When top component  310  is rotationally aligned with bottom component  350  and top component  310  and bottom component  350  are pushed together, clips  360  actuate and couple top component  310  with bottom component  350 . In some embodiments, clips  360  are distributed every 90° around the perimeter of top component  310 . Once coupled together via the clips, top component  310  and bottom component  350  may be separated again by pulling the two components apart or, in some embodiments, the clips are configured to permanently engage such that top component  310  and bottom component  350  cannot be separated (without damage). 
     In some embodiments, rotational alignment extrusion  370 - 1  is present. Rotational alignment extrusion  370 - 1  may be part of either top component  310  or bottom component  350 . In the illustrated embodiment of smoke chamber  300 , rotational alignment extrusion  370 - 1  is part of top component  310 . Rotational alignment extrusion  370 - 1  may serve to ensure that, when top component  310  is coupled with bottom component  350 , the two components are properly rotationally aligned. Rotational alignment extrusion  370 - 1  may, when properly aligned, insert into rotational alignment gap  371 - 1  which is present on bottom component  350 . It should be understood that in other embodiments, rotational alignment gap  371 - 1  may be located on top component  310  and rotational alignment extrusion  370 - 1  may be located on bottom component  350 . It is also possible that, in some embodiments, more than one rotational alignment extrusion and more than one rotational alignment gap may be present. If multiple rotation alignment extrusions are present, the shapes of such rotational alignment extrusions and corresponding rotational alignment gaps may be distinct such that a rotational alignment extrusion can only be inserted into a particular corresponding rotational alignment gap. 
     On top component  310 , groove  320  may be present. Groove  320  may be present to decrease an amount of material necessary to mold top component  310 . Top component  310  and bottom component  350  may each be molded out of plastic or some other material. As such, the less material used in making top component  310  and/or bottom  350 , the less it may cost to manufacture smoke chamber  300 . 
     Smoke chamber  300  may be designed such that EM sensor  330  senses EM radiation within an airspace present within smoke chamber  300 . One or more EM emitters, such as EM emitters  340 - 1  and  340 - 2  may be positioned to emit EM radiation into the airspace within smoke chamber  300 . EM emitters  340 - 1  and  340 - 2  may emit EM radiation at different wavelengths. For example, one of EM emitters  340  may emit infrared radiation while the other EM emitter may emit blue light. EM sensor  330  may only detect emitted EM radiation when particulate matter is present within smoke chamber  300  to deflect such emitted EM radiation into a field of view of EM sensor  330 . While the illustrated embodiment of smoke chamber  300  uses two EM emitters, it should be understood that other embodiments of smoke chamber  300  may be configured for more than two EM emitters or a single EM emitter. Similarly, smoke chamber  300  is illustrated as having only a single EM sensor  330  partially inserted into smoke chamber  300 . Other embodiments may use multiple EM sensors. 
     Greater detail regarding embodiments of top component  310  is provided in relation to  FIGS. 4-7 . Greater detail regarding embodiments of bottom component  350  is provided in relation to  FIGS. 4, 5, and 8-11 . 
       FIG. 4  illustrates smoke chamber  400  separated into constituent parts. It should be understood that smoke chamber  400  can represent smoke chamber  300  separated into its constituent parts and/or can represent any other smoke chamber discussed in this document. Smoke chamber  400  is decoupled into its constituent parts: top component  310  and bottom component  350 . Also illustrated in embodiment 400 are EM emitters  340  and EM sensor  330 . As detailed in relation to  FIG. 3 , clips  360  are permanently part of top component  310 . Clips  360 - 1  may be configured to detachably or non-detachably couple with bottom component  350  when inserted into clip channels  420  (e.g., clips channels  420 - 1 ,  420 - 2 ,  420 - 3 , etc.). When inserted into clip channels  420 , clips  360  may clip to a portion of clip lip  425 . It should be understood that a clip channel may be present for each clip of clips  360  present on top component  310 . 
     Present on top component  310  may be airflow fins  410 . Airflow fins may serve to channel airflow towards the center of the airspace within smoke chamber  400 . Each of airflow fins  410  may be radially aligned with a center point or center axis (center axis  500  of  FIG. 5B ) of top component  310  (or, more generally, smoke chamber  400 ). Airflow fins  410  may be located along an airflow surface  430  of top component  310 . Each airflow fin of airflow fins  410  may be curved to follow airflow surface  430  and the resulting airflow path that leads from the external environment to the airspace within smoke chamber  400 . Airflow fins  410  may be distributed at regular intervals around the curved airflow surface  430 . The curved airflow surface  430  may radially curve outward from the center or center axis of top component  310 . The outer perimeter of airflow surface  430  may be circular, each airflow fin may be evenly distributed on airflow surface and radially aligned with a center axis of top component  310 . Airflow fins  410  may be sized such that, when top component  310  is coupled with bottom component  350 , airflow fins  410  occupy the full height of an airflow channel between the airspace within smoke chamber  400  and the external environment. 
     In some embodiments, eight airflow fins are present and are equally distributed at 45° angles as measured from a center axis of top component  310 . In other embodiments, a greater or fewer number of airflow fins may be present. In the illustrated embodiment, airflow fins are either free standing (e.g., airflow fin  410 - 2 ) and molded to top component  310 , molded to a clip (e.g., airflow fin  410 - 1  partially molded to clip  360 - 1 ) and molded to top component  310 , or molded to a rotational alignment extrusion (e.g., airflow fin  410 - 3  partially molded to clip  360 - 3 ) and molded to top component  310 . As such, rotational alignment extrusion  370 - 1  may be positioned at a 45° angle on top component  310  relative to clips  360 . 
     On airflow surface  430 , which is generally curved, a series of steps  440  set at 90° angles or approximately 90° angles to each other may be present. Such steps may be circular in that they are concentrically arranged around a central axis of top component  310  (central axis  599  of  FIG. 5B ). Steps  440  may be interrupted at the locations where airflow fins  410 , clips  360 , and/or rotational alignment extrusion  370 - 1  are molded to top component  310 . Steps  440  vary in height and depth such as to mirror the radially-outward curve of airflow surface  430 . Circular steps  440  may serve to help prevent light from the external environment from being reflected off of airflow surface  430  into the airspace of smoke chamber  400 . In some embodiments, at least ten steps are present; in other embodiments, twelve, fifteen, or some smaller or greater number of steps are present. 
     Encircling the airspace within smoke chamber  400  may be airspace ribs  450 . Airspace ribs may completely encircle the portion of the airspace housed by top component  310 . Airspace ribs  450  may serve to obscure reflection of EM radiation incident on such airspace ribs  450  by helping to prevent such EM radiation from being reflected back into the airspace and, more specifically, toward EM sensor  330 . Airspace ribs may be triangular in that each rib includes two flat sides that meet at an angle (the third side being part of a curved wall that forms the airspace). 
     Referring now to bottom component  350 , clip lip  425  may at least partially encircle bottom component  350 . Clip lip  425  may, in some embodiments, only be present in the vicinity of clip channels  420  to allow clips  360  to couple with bottom component  350 . Referring to the rotational alignment gaps, rotational alignment gap  371 - 1  has a different perimeter than rotational alignment gap  371 - 2  such as to correspond to a particular rotational alignment extrusion of top component  310 . 
     EM sensor  330  and EM emitters  340  may be partially inserted into bottom component  350 . Anchor bay  365 - 1  may receive EM sensor  330  and allow it to sense EM radiation within the airspace of smoke chamber  400 . Anchor bay  365 - 2  may receive EM emitter  340 - 1  and allow it to emit EM radiation into the airspace of smoke chamber  400 . Anchor bay  365 - 3  may receive EM emitter  340 - 2  and allow it to emit EM radiation into the airspace of smoke chamber  400 . Anchor bays  365  may be sized such that EM sensor  330  and EM emitters  340  fit tightly to limit EM leakage of EM radiation into or out of the airspace of smoke chamber  400  between an edge of anchor bays  365  and EM sensor  330  and EM emitters  340 . 
     Present at and around a center point of bottom component  350  may be dust collector  460 . Dust collector  460  may be positioned directly below a center point of where the emitted EM radiation from EM emitters  340  intersects the field of view of EM sensor  330 . Dust collector  460  may be a depressed portion of bottom component  350 . Dust collector  460  may be below a field of view of the EM sensor. In some embodiments, dust collector  460  may be a pentagonal shape; in other embodiments, other shapes, such as a circular shape, may be used. Dust collector  460  may serve to collect any small particles that have entered smoke chamber  400  and have settled (i.e. are no longer suspended in air). Dust collector  460  may help prevent such particles from interfering with or causing a false positive of smoke detection by deflecting EM radiation emitted by EM emitters  340 . 
       FIGS. 5A and 5B  illustrate a cross section of an embodiment of the smoke chamber of  FIGS. 3 and 4 . The embodiments of smoke chambers  500 A and  500 B, which represent cross sections of the previously detailed smoke chambers  300  and  400 , are discussed in parallel below. The features discussed in relation to smoke chambers  500 A and  500 B may be present in any of the detailed smoke chambers within this document. Smoke chambers  500 A and  500 B are shown with the top component and bottom component coupled. The three-dimensional airspace  580 , loosely outlined in  FIG. 5B , represents the airspace present within smoke chambers  500 A and  500 B. 
     Top platter  510  serves as the ceiling of smoke chambers  500 A/ 500 B. The exterior surface of top platter  510  may generally be flat. This allows a flat metallic cap to be placed against top platter  510  to help isolate all EM sensors from external EM radiation. The radial outward curve of airflow surface  430  is readily available in the cross-section of  FIG. 5A . Further, as can be seen, steps  440  are located upon the surface of airflow surface  430 . Also clearly visible is groove  320  which encircles top platter  510 . Airflow path  520  for airflow into and out of airspace  580  is represented by a dotted arrow. It should be understood that this path for airflow generally encircles airspace  580 . The path for airflow may be interrupted by structures such as clips  360 , airflow fins  410 , and rotational alignment extrusions  370 . 
     In order to maintain a high level of airflow, a minimum width for the airflow path may be maintained between airflow surface  430  and airflow surface  530 . For instance, the minimum height of the airflow channel may be 3 mm. Therefore, at locations such as  521  and  522 , the distance between airflow surface  430  and airflow surface  530  may be at least 3 mm. In other embodiments, a smaller or greater minimum distance between the two airflow services may be maintained. Further, airflow surfaces  430  and  530  are positioned relative to each other such that a direct path does not exist for light from the external environment to enter airspace  580  (or, if it does exist, allows for very little light to enter the airspace). 
     While airflow surface  430  is covered in a series of steps  440 , airflow surface  530  may not be covered in such steps. This may allow stray EM radiation from within airspace  580  to more readily be reflected off airflow surface  530  out of airspace  580 . Therefore, while the step surface of airflow surface  430  is intended to prevent EM radiation from entering smoke chamber  500 , airflow surface  530  may be curved to promote EM radiation to reflect off the surface of airflow surface  530  and exit smoke chamber  500 A/ 500 B. In some embodiments, airflow surface  530  is polished to promote reflection out of the smoke chamber. 
     In some embodiments, at least a portion of airflow surface  530  and interior surface  531  is polished. By having these surfaces polished, reflections on such surfaces may be more predictable and can more consistently be handled, thus, helping to limit false positive detections of smoke. 
     Offset angle  550  represents an offset angle between an emission path of emitter  340 - 1  and the field of view of the EM sensor. It may be desirable for such an offset angle to be present such that each EM emitter of EM emitters  340  does not directly emit EM radiation into a field of view of the EM sensor. Rather, EM radiation needs to be deflected off particulate matter, such as smoke, in order to be sensed by an EM sensor. The offset angle can affect performance of when smoke is detected within smoke chamber  500 A/ 500 B. In some embodiments, offset angle  550  between the EM emitters and the EM sensor is 40°. In such embodiments, the EM emitters are symmetrically offset at an from the EM sensor. At such an offset angle, a large amount of discrimination between particle sizes less than 300 nanometers may be attained. Within a range of approximately 35° to 45° has been found to be effective for forward scatter sensing of smoke particulate matter. 
     The bottom component of smoke chamber  500 A may have emitter/sensor holders, such as emitter/sensor holder  540 - 1 . Emitter/sensor holder  540 - 1  may serve to hold and anchor one or more leads of an EM sensor or EM emitter, such as EM emitter  340 - 1 . Emitter/sensor holder  540 - 1  may serve to help hold EM emitter  340 - 1  in place such that EM emitter  340 - 1  remains properly inserted within its anchor bay. Emitter/sensor holders  540  may have gaps that receive leads of EM sensors and emitters. Once inserted, friction and/or the emitter/sensor holder partially deforming, may help hold the sensor/emitter in place. 
     Further, in  FIG. 5B , central axis  599  is represented. This axis represents the center of the top and bottom components. Various components of both the top and bottom components are arranged in concentric patterns about central axis  599 . 
       FIG. 6  illustrates an angular projection of an embodiment of a top component  600  of the smoke chamber. Top component  600  is shown inverted in  FIG. 6 . Top component  600  may represent any of the previously detailed top components of the various detailed smoke chambers or any other top component discussed in this document. Visible in top component  600  are pyramidal extrusions  610 . Pyramidal extrusions  610  may serve to limit reflection of EM radiation incident on the internal top surface of top component  600 . Pyramidal extrusions  610  may have three or four sided extrusions. Pyramidal extrusions  610  may be arranged in roughly a circular pattern around a center point of top component  600 . Dozens or hundreds of pyramidal extrusions  610  may be present. Pyramidal extrusions  610  may be molded as part of top component  600  (as may all other components of top component  600 ). While the extrusions are pyramidal in the illustrated embodiment of  FIG. 6 , it should be understood that the extrusions may be in some other shape (e.g., conical) and serve a similar purpose of limiting reflected EM radiation. 
     On the opposite side of top component  600  from rotational alignment extrusions  370 - 1  is a second extrusion referred to as rotational alignment extrusions  370 - 2 . In some embodiments, rotational alignment extrusion  370 - 2  is at a 180° angle to rotational alignment extrusion  370 - 1  around top component  600 . Rotational alignment extrusion  370 - 2  may be a length different from rotational alignment extrusion  370 - 1  in order to couple with a different sized rotational alignment gap of a corresponding bottom component. Additionally or alternatively, and as illustrated in  FIG. 6 , rotational alignment extrusion  370 - 2  is attached to a differently shaped airflow fin  410 - 5 . Airflow fin  410 - 5 , rather than mirroring the shape of the airflow path created by the airflow surface of the corresponding bottom component, instead forms a fin to be inserted through a slot at a corresponding location in a bottom component. As such, for top component  600  to be clipped to a corresponding bottom component, at least rotational alignment extrusion  370 - 1 , rotational alignment extrusion  370 - 2 , and airflow fin  410 - 5  need to be properly rotationally aligned with the corresponding bottom component. 
       FIG. 7  illustrates a bottom view of an embodiment of a top component  700  of the smoke chamber. Top component  700  is illustrated inverted. Top component  700  may represent any of the previously detailed top components of the various detailed smoke chambers or the top chamber of any other smoke chamber detailed in this document. Visible in top component  700  are pyramidal extrusions  610 . In the illustrated embodiment, pyramidal extrusions  610  are arranged in rows and columns that are angularly offset from being aligned with any airflow fin, such as airflow fin  410 - 4 . In other embodiments, pyramidal extrusions  610  may be aligned with one or more airflow fin. 
     Steps  440  are visible as encircling the airflow surface of top component  600 . Steps  440  form concentric circles around a center axis of top component  600  along the airflow surface, steps  440  being interrupted by airflow fins  410  (e.g.,  410 - 4 ), clips  360 , and rotational alignment extrusions  370 . 
     In the illustrated view of top component  700 , airspace ribs  450  can be seen as fully encircling the airspace formed by the interior of top component  700 . Airspace ribs  450  may be parallel and concentric around the central axis (e.g., central axis  599 ) of top component  700 . In other embodiments, airspace ribs may not be parallel with the central axis and/or may not fully encircle the airspace formed by the interior of top component  700 . 
       FIG. 8  illustrates an angular projection of an embodiment of the bottom component  800  of the smoke chamber. Bottom component  800  may represent any of the previously detailed bottom components of the various detailed smoke chambers or any other bottom component detailed in this document. Visible in bottom component  800 , as illustrated, are bay rib regions  810  (e.g., bay rib regions  810 - 1 ,  810 - 2 ,  810 - 3 ). Bay rib regions  810  may only be located above anchor bays  820 , of which in the illustration of  FIG. 8  only anchor bay  820 - 1  is visible. An anchor bay of anchor bays  820  are where EM emitters and EM sensors are inserted in order to emit or sense EM radiation within the airspace of the smoke chamber formed by bottom component  800 . Bay ribs of bay ribs regions  810  may serve to prevent reflection of EM radiation incident upon them. Bay ribs of bay ribs regions  810  may be parallel to a central axis of bottom component  800 , such as central axis  599  of  FIG. 5B . In other embodiments, Bay ribs of bay ribs regions  810  may not be parallel to such a central axis. Bay ribs of bay ribs regions  810  may be present as opposed to a smooth, polished surface (e.g.,  530 ) due to constraints of the manufacturing process. As with the various detailed top components, the various detailed bottom components, including bottom component  800 , may be molded as a single piece of material, such as (polycarbonate) plastic. 
     Depressed within the bottom internal surface of bottom component  800  may be bottom channels  830 . A stand-alone bottom channel  830 - 1  may be present for the EM sensor (which is to be inserted in anchor bay  820 - 1 ). Bottom channels  830 - 2  and  830 - 3  may meet and merge away from the anchor bays for the EM emitters. Bottom channels  830  may be depressed so as to decrease a likelihood that a buildup of particulate matter (e.g., dust) affects sensing of EM radiation within the smoke chamber. The surface of bottom channels  830  may be polished. Each of bottom channels  830  may be directed from its respective anchor bay toward the central axis of bottom component  800 . Bottom channels  830  may end and meet at dust collector  460 . Internal surface  840 , like airflow surface  530 , may be smooth and polished. Embodiments are possible in which internal surface  840  may be rough to obscure reflections. 
       FIG. 9  illustrates a top view of an embodiment of the bottom component  900  of the smoke chamber. Bottom component  900  may represent any of the previously detailed bottom components of the various detailed smoke chambers. Visible in  FIG. 9  are rotational alignment gaps  371 . Rotational alignment gap  371 - 1  is configured to receive an extrusion, while rotational alignment gap  371 - 2  is configured to receive a rotational alignment extrusion and elongated fin. Such rotational alignment gaps allow bottom component  900  to be coupled with a top component in one particular rotational alignment. Also visible in bottom component  900  are bottom channels  830 . In the illustrated embodiment of bottom component  900 , two bottom channels for EM emitters are present and a single channel for an EM sensor is present. EM channels  830 - 2  and  830 - 3  are aimed towards a center axis of bottom component  900 . Wedge isolator  910  is a piece of material (e.g., part of the molded bottom component  900 ) that helps isolate the two EM emitter anchor bays from each other. Just as a vertical offset angle  550  was discussed in relation to  FIG. 5A , a horizontal offset angle may be present between the two emitter anchor bays. Horizontal offset angles  920  ( 920 - 1 ,  920 - 2 ) are in a plane perpendicular to central axis  599 . In some embodiments, each of these angles is 20 degrees. Offset angles  920  may be the same or may be different angles. Various embodiments may have any angle between 10 and 35 degrees for each of offset angles  920 . The angles of  920 - 1  and  920 - 2  may vary from each other. 
       FIG. 10  illustrates a side view of an embodiment of the bottom component  100  of the smoke chamber. Bottom component  1000  may represent any of the previously detailed bottom components of the various detailed smoke chambers.  FIG. 11  illustrates an angular view of an embodiment of the bottom component  1100  of the smoke chamber. Bottom component  1100  may represent any of the previously detailed bottom components of the various detailed smoke chambers. Bottom components  1000  and  1100  are described together as follows. Emitter/sensor holder  540 - 3  serves to hold an EM sensor in place such that the sensor&#39;s field of view is through aperture  1010  and therefore has a view of the airspace within the smoke chamber formed using bottom component  1000 . Aperture  1010  is rectangular in shape within the circular opening of anchor bay  365 - 1 . Aperture  1010  may be adjusted in height and width to control the field of view of the EM emitter inserted within the circular opening of anchor bay  365 - 1 . While the illustrated embodiment is focused on an EM sensor, a similar aperture may be present for one or more of the anchor bays for EM emitters. Each EM emitter anchor bay may have a same aperture as  1010 , may have an aperture specific to the EM emitters, or may have an aperture selected for the specific wavelength of the EM radiation emitted by the particular EM emitter (that is, the aperture used for each EM emitter may vary). In other embodiments, the apertures and/or the aperture for either or both of the EM emitters may be another shape, such as circular, square, oval, etc. 
     Also present within anchor bay  365 - 1  may be crush ribs  1020  (e.g., crush rib  1020 - 1 ,  1020 - 2 ). Crush ribs  1020  may help secure an inserted EM sensor within the opening of anchor bay  365 - 1 . When an EM sensor is inserted into the circular opening, crush ribs  1020  may be partially deformed and may exert pressure and cause friction on the EM sensor. Therefore, emitter/sensor holder  540 - 3  and crush ribs  1020  may function in concert to hold an EM sensor in place. It should be understood that other anchor bays  365  (e.g., for EM emitters) may have similar arrangements of crush ribs. In the illustrated embodiment, three crush ribs  1020  are equally distributed at 120 degree angles around the circular opening of anchor bay  365 - 1 ; it should be understood that in other embodiments, fewer or greater numbers of crush ribs  1020  may be used for securing the EM sensor. 
       FIG. 12A  illustrates an embodiment of a mesh  1200 A that can be wrapped around the various detailed embodiments of smoke chambers to prevent large particulate matter (e.g., bugs, dust) from entering the smoke chamber. Such large particulate matter, if in the smoke chamber, may result in a false detection of smoke, leading to an alarm being sounded when no smoke or fire is present. Referring to  FIGS. 5A and 5B , mesh  1200 A may be wrapped around smoke chambers  500 A/ 500 B such that airflow path  520  is fully encircled by mesh  1200 A. As such, all airflow entering (and exiting) interior  580  passes through mesh  1200 A. Chamber shield may include one or more solder tabs to allow mesh  1200 A to be attached by solder to a circuit board. 
     Mesh  1200 A may be conductive. More specifically mesh  1200 A may be metallic. Mesh  1200 A is further represented by first mesh end  1200 B of  FIG. 12B  and second mesh end  1200 C of  FIG. 12C . First mesh end  1200 B (which represents the left end of mesh  1200 A) contains tab joint  1201  which is configured to receive tab  1202  of second mesh end  1200 C (which represents the right end of mesh  1200 A) when mesh  1200 A is wrapped around a smoke chamber. While tab  1202  and tab joint  1201  represent one possible embodiment of how the ends of mesh  1200 A can be joined together, it should be understood that other attachment methods and/or mechanisms can be used (e.g., glue, clips, etc.). Present on mesh  1200 A and visible on first mesh end  1200 B and second mesh end  1200 C is a hexagonal mesh pattern  1203  that allows substantial airflow through mesh  1200 A. Each hexagonal mesh hole may be between 0.1 mm and 2 mm in average width. It should be understood that other mesh patterns are possible, including circular mesh patterns, rectangular mesh patterns, etc. 
     Mesh  1200 A may function in concert with chamber shield  289 , which can serve as a conductive (e.g., metallic) cap over the smoke chamber. A conductive base, which may be a field of solder present on an underlying circuit board or a conductive barrier similar to chamber shield  289 , may be present on the opposite side of a smoke chamber such that the smoke chamber is surrounded by a conductive barrier. This conductive barrier, which serves as a Faraday cage, can serve to decrease an amount of EM noise (generated by external sources) sensed by the EM sensor present within the smoke chamber. Mesh  1200 A may be manufactured as a single piece of metal that includes a chamber shield  289 . A tab may be bent such to allow chamber shield  289  to be placed atop a smoke chamber. 
     In some embodiments, mesh  1200 A is connected with chamber shield  289  by the two components being formed from a single piece of metal and connected via tab  1205 . Chamber shield  289  may be folded over the top of a smoke chamber while the remainder of the mesh  1200 A is wrapped around the smoke chamber. In some embodiments, on the opposite side of the smoke chamber from chamber shield  289 , the smoke chamber may not be fully encased in a conductive shield. Rather, only a portion of the smoke chamber proximate to the location of the EM sensor may be wrapped in a conductive material. Such an arrangement may decrease the total amount of conductive material that needs to be used to effectively provide a Faraday cage around the EM sensor. 
     Different types of fires can produce particulate matter of different sizes. For instance, a highly energetic flaming fire may tend to produce smaller smoke particles while a less energetic, smoldering fire may tend to produce larger smoke particles. It is important for a smoke detector to be able to detect all of such types of fires early enough (e.g., to allow persons to escape the situation, protect private property from burning). To be able to do so effectively, using multiple wavelengths of light within a smoke chamber may be beneficial. That is, certain wavelengths of light may work better for detecting particulate matter of certain size ranges, as the closer match between wavelength and mean particle size can result in higher scattering efficiency. For instance, infrared light may work well for large smoke particles while blue light may work well for smaller smoke particles. 
     Inside a smoke chamber there can be a large number of smoke particles, encompassing a multitude of shapes, compositions, and sizes. Therefore, density distributions can be used to model the size, shape, and permittivity of the particulate matter. The shape and permittivity of the smoke chamber itself, as well as the spectral characteristics of the EM emitter(s) and EM sensor (e.g. photodetector), all play a role in how much reflected or deflected EM radiation can be detected by the EM sensor. 
     In general, smoke produced by a specific material (e.g., liquid fuel, paper, cotton, wood) has a characteristic density distribution. The presence of flames (flaming fires) or lack thereof (smoldering fires) and the environmental conditions (e.g., humidity, temperature) have a direct influence on the thermodynamic environment of the event and can affect the transport of smoke particulate matter. At one extreme, smoke can be very energetic and quickly propagate through an environment and find its way to a smoke detector device quickly. On the other end of the spectrum, some smoldering fires can produce large quantities of low energy smoke that stratifies near or several feet above a floor of a room and a significant amount of time can elapse before enough smoke particles propagate far enough to reach the smoke detector. 
     By using multiple wavelengths of EM radiation to detect smoke particles, it can become possible (up to a point) to differentiate between different kinds of fires by creating incident fields centered at specific wavelengths. For instance, using EM radiation at significantly different wavelengths (e.g., wavelengths near the opposite ends of the visible light spectrum, such as blue and infrared EM radiation), it may be possible to identify the type of fire causing the smoke. 
     The smoke chambers, along with the EM emitters and EM sensors, previously detailed can be used to perform various methods of smoke detection. Various methods may involve using multiple EM emitters in combination with an EM sensor and an embodiment of a smoke chamber as previously detailed in relation to  FIGS. 3-12 . Referring to  FIG. 2C , device  200 C may perform the methods of  FIGS. 13-16 . Other forms of devices, such as a dedicated smoke detector having a smoke chamber, may perform the methods of  FIGS. 13-16 . As detailed in relation to  FIG. 17 , a system that includes a smoke chamber, two (or more) EM emitters, an EM sensor, and a processing system may perform the methods of  FIGS. 13-16 . In some embodiments, system  1700  of  FIG. 17  may be part of device  200 C. 
       FIG. 13  illustrates an embodiment of a method  1300  for using two modes for monitoring for smoke in a smoke chamber. “Mode” refers to a state of the device controlled by an on-board processing system of the device. Based on the device&#39;s mode, the multiple (i.e., two or more) EM emitters may emit light in different patterns. In some modes, only a single EM emitter is used and the other EM emitter(s) is/are disabled. In some modes, a frequency of enabling of the EM emitters is controlled. Generally speaking, as a level of detected smoke in an environment increases and approaches an alarm limit, the more frequently and accurately the smoke level in the environment should be monitored. While the following description focuses on enabling and disabling EM emitters, it should be understood that an EM sensor&#39;s enablement pattern may mirror the EM emitters such that an EM sensor is only powered when an EM emitter is illuminated. In other embodiments, the EM sensor may remain continuously powered and activated. In still other embodiments, the EM sensor may be enabled for longer in duration than the EM emitters, but may still be disabled on a periodic basis to save power and/or prolong the life of the EM sensor. 
     In reference to  FIG. 13 , two modes are detailed. The first mode may be activated at the device when the detected smoke level is below a defined, stored threshold level or no smoke is detected. The second mode may be activated at the device when the detected smoke level is above the defined, stored threshold level or some level of smoke is detected. Generally, it may be desirable for the device to be in the first mode as compared to the second mode, because the first mode has one or more EM emitters activated less often. By one or more EM emitters being activated less often, less power is consumed and, possibly, the lifetime of the one or EM emitters is extended. For instance, an EM emitter, which can be in the form of a light emitting diode (LED), can be expected to last for roughly a defined period of time before the EM emitter either stops functioning or its optical output degrades (e.g., in intensity) such that it can no longer reliably be used for the detection of smoke particles. 
     At block  1310 , the smoke detector may be set to a first mode. Setting the smoke detector device to a first mode may take the form of a processing system of the smoke detector storing an indication to memory indicative of the first mode being active. The processing system may control the multiple EM emitters and EM sensor in accordance with a sensing definition of the first mode, as defined below. The smoke detector may be set to the first mode at block  1310  based on: previous measurements of smoke indicating that a threshold level of smoke has not been exceeded, evaluation of a metric that indicates that smoke in the environment is below a threshold, or the smoke detector recently being activated or reset. 
     At block  1320 , the device may monitor for smoke in the first mode. In some embodiments, monitoring for smoke in the first mode occurs as detailed in relation to method  1500  of  FIG. 15 : only one EM emitter is periodically activated for detecting whether smoke is present in the smoke chamber while at least one other EM emitter is kept disabled (except, possibly, for periodic self-testing). In other embodiments, monitoring for smoke in the first mode occurs as detailed in relation to method  1600  of  FIG. 16 : at least two EM emitters are alternatingly used for assessing an amount of smoke in the smoke chamber with a period of time being waited between illumination with all EM emitters disabled. 
     At block  1330 , the mode of the smoke detector may be determined. This determination may be based on information gathered while monitoring for smoke at block  1320 . Therefore, based on information gathered at block  1320  while monitoring for smoke, the mode of the smoke detector at block  1330  will either be maintained by remaining in first mode and returning to block  1320  or will be modified to a second mode and method  1300  will proceed to block  1340 . 
     To determine the mode for the smoke detector, a metric value may be calculated. For instance, when an embodiment of method  1600  is being used as the first mode, equation 1 may be used to calculate a metric value for use in determining the mode of the smoke detector. When operating in accordance with method  1600 , with the two EM emitters alternatingly turned on, two voltage values may be output by the EM sensor based on EM radiation sensed when each EM emitter is individually turned on. This voltage value may be converted into dB/m. 
       Metric=ired scaling *ired level +blue scaling *blue level   Eq. 1
 
     The unit of measurement on the measured levels of infrared (abbreviated ired) and blue light as detected by the EM sensor can be dB/m. In equation 1, ired scaling  and blue scaling  are scaling factors that are selected by the manufacturer and programming into the device to strike a balance between alarming as early as possible when smoke is present while still complying with established regulations. Since the device can be network-enabled, it should be understood that the scaling factors, along with the use of equation 1, can be adjusted by a service provider after the device has been installed in a user&#39;s structure (e.g., home, office, etc.). Therefore, the ability to accurately and quickly detect smoke can be improved over time by providing the device with an updated algorithm and/or scaling factors. In some embodiments, the ired scaling  scaling factor used is 4 and the blue scaling  scaling factor used is 1. 
     Metric is a function of time (that is, the calculated value of Metric will change as additional measurements are made at block  1320  at different times). The value of Metric can be expected to increase rapidly or slowly, depending on the type of fire and other environmental conditions. The instantaneous value of Metric can be compared against one or more predefined thresholds. The results of these comparisons may be fed into individual rolling windows for evaluation of whether an alarm should be output, a warning should be output, or other action should be taken. When a large enough number of positives has been detected in a given window, a corresponding action is performed. For example, a positive input (e.g., 1) may be entered into a sliding window calculation when the calculated metric is greater than a predefined threshold value, such as 0.15. A negative input (e.g., 0) may be entered into the sliding window calculation when the calculated metric is less than 0.15 or whatever the predefined threshold value is. When a window target value is reached, such as 2 or greater, an event may be performed. 
     Table 1 lists various windows that may be monitored using the Metric value. The threshold indicates the threshold value against which Metric is compared for generating a positive or negative input to the window. The window target value indicates a summation value that must be reached by the summation of the entries in the window in order to trigger a response or other form of action. Window size indicates the number of Metric inputs that are maintained as part of the rolling window. Window span indicates the amount of time in seconds covered by the window. As an example, as noted in Table 1, UT_warning requires at least two out of five positives to yield a true condition; otherwise UT_warning has a false condition. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                 Window  
               
               
                   
                 Threshold 
                 Window  
                 Window  
                 Span 
               
               
                 Window Name 
                 (dB/m) 
                 Target 
                 Size 
                 (seconds) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Monitor (fast/slow 
                 0.1 
                 1 
                 5 
                 10 
               
               
                 sampling) 
                   
                   
                   
                   
               
               
                 UT warning 
                 UT_threshold 
                 2 
                 5 
                 10 
               
               
                 LT warning 
                 LT_threshold 
                 5 
                 5 
                 10 
               
               
                 Alarm_CO_present 
                 0.238 
                 6 
                 10 
                 20 
               
               
                 Alarm_CO_absent 
                 0.330 
                 6 
                 10 
                 20 
               
               
                 Alarm_exit 
                 0.135 
                 10 
                 10 
                 20 
               
               
                   
               
            
           
         
       
     
     As noted in Table 1, similar rolling windows may be used for determining whether other conditions are present. For example, Alarm_CO_present may be used to determine when to output an alarm when CO (measured using a CO sensor and compared to a threshold value) has been identified as present in the environment. An alarm may be triggered when Alarm_CO_present is positive. Alarm_CO_absent may be used to determine when to output an alarm when CO (measured using a CO sensor) has been identified as not being present in the environment. An alarm may be triggered when Alarm_CO_absent is positive. If CO is measured as present in the environment, the alarm triggers based on a lower Metric value than if CO is not present. 
     In Table 1, UT_warning (Upper Threshold warning) and LT_warning (Lower Threshold warning) represent target values associated with the issuance of a warning (as opposed to an alarm) and exiting an existing warning condition, respectively based on the value of Metric. The number of positives within the respective windows needed to satisfy a warning exit criteria may be larger than that needed to trigger a warning condition. In the case of LT_warning, a positive would be generated when a value is measured below LT_threshold; while in the case of UT_warning, a positive would be generated when a value is measured above UT_threshold. Such an arrangement can prevent the device from repeatedly “bouncing” between a warning and non-warning state. Alarm_exit represents a target value associated with exiting an alarm (as opposed to a warning) condition. The number of positives required to exit the alarm condition may be larger than the number needed to trigger an alarm condition, to prevent bouncing. In the case of Alarm_exit, a positive would be generated when a Metric value is measured below the noted threshold for the target number of samples within the window. 
     Monitor may use the Metric as evaluated in a rolling window to determine a speed of sampling of red and blue light measurements within the smoke chamber. When the threshold is exceeded for the window target number of samples within the window size, fast sampling may be enabled; otherwise it may be disabled. It should be understood that the values used within Table 1 are merely exemplary and may be increased or decreased to alter when the device outputs warnings and/or alarms. 
     For instance, windows may be monitored to determine when an alarm should be output and when a warning should be output. To be clear, an “alarm” refers to a condition typically associated with a loud noise being created by a smoke detector signaling to persons nearby that smoke is present. The amount of smoke necessary for an alarm to be triggered is typically defined by law or regulation. “Warning” refers to a condition that involves less smoke being detected. A warning level may not be defined by law or regulation, but may be implemented by a smoke detector manufacturer to warn persons nearby that the level of smoke in the environment is rising and that, if the smoke level keeps rising, the alarm condition will occur. A warning may result in a recorded or synthesized auditory message being output by the smoke detector device warning the user of the smoke level; an alarm is typically associated with a loud buzzing sound. 
     At block  1330 , if the value of Metric is above a particular Metric threshold , such as 0.04 or 0.1; the second mode may be entered and method  1300  proceed to block  1340 . Otherwise, method  1300  returns to block  1320 . To be clear, the modes of operation of methods  1300  and  1400  may be calculated separately from whether a warning or alarm threshold is crossed according to the rolling windows. For instance, in some embodiments, triggering of an output of either a warning or alarm will only occur once Metric has been sufficiently large enough in magnitude to already place the smoke detector in the second mode of method  1300  or third mode of method  1400 . 
     At block  1340 , the smoke detector may be set to a second mode. Setting the smoke detector device to a second mode may take the form of a processing system of the smoke detector storing an indication to memory indicative of the second mode now being active. The processing system may control the multiple EM emitters and EM sensor in accordance with a sensing definition of the second mode, as defined below. 
     At block  1350 , the device may monitor for smoke in the second mode. The second mode differs in at least some respect from the first mode. In some embodiments, if monitoring for smoke in the first mode occurs as detailed in relation to method  1500  of  FIG. 15 , monitoring for smoke in the second mode occurs as detailed in relation to method  1600  of  FIG. 16 . In other embodiments, if monitoring for smoke in the first mode occurs as detailed in relation to method  1600  of  FIG. 16 , monitoring for smoke in the second mode may also occur as detailed in relation to method  1600 , but the period of time between alternating EM emissions may be changed (e.g., decreased). 
     At block  1360 , the mode of the smoke detector may again be determined. This determination may be performed in the same manner as at block  1330 . Based on information gathered while monitoring for smoke at block  1350 , a determination may be made as to whether the smoke detector should remain in the second mode (and return to block  1350  for additional monitoring) or the mode of the smoke detector should be set to the first mode at block  1310 . Therefore, based on information gathered at block  1350  while monitoring for smoke, the mode of the smoke detector at block  1360  will either be maintained by remaining in second mode and returning to block  1350  or will be modified to the first mode and method  1300  will proceed to block  1310 . Just as at block  1330 , the Metric value may be calculated and used for determining the mode of the smoke detector, either by direct comparison to a threshold value or by comparing the number of times that the metric value exceeds a threshold value during a sliding window to one or more threshold percentages for a warning or alarm level. 
       FIG. 14  illustrates an embodiment of a method  1400  for using three modes for monitoring for smoke in a smoke chamber. Method  1400  may be focused on a smoke detector that uses a first mode when no smoke or very little smoke is detected, a second mode when some smoke is detected, and a third mode when more smoke is detected. Again, it may be desirable for the device to be in the first mode as compared to the second mode or the third mode, because the first mode has one or EM emitters activated less often. By one or more EM emitters being activated less often, less power is consumed and, possibly, the lifetime of the one or EM emitters is extended. For instance, an EM emitter, which can be a form of light emitting diode (LED), can be expected to last for about a defined period of time before the EM emitter either stops functioning or its optical output degrades (e.g., in intensity) such that it can no longer reliably be used for the detection of smoke particles. Similarly, the second mode as detailed in relation to  FIG. 14  may be preferable to the third mode for the same reasons. 
     At block  1405 , the smoke detector may be set to a first mode. Setting the smoke detector device to a first mode may take the form of a processing system of the smoke detector storing an indication to memory indicative of the first mode being active. The processing system may control the multiple EM emitters and EM sensor in accordance with a sensing definition of the first mode, as defined below. The smoke detector may be set to the first mode at block  1405  based on: previous measurements of smoke indicating that a threshold level of smoke has not been exceeded, evaluation of Metric that indicates that smoke in the environment is below a low threshold (e.g., 0.04), or the smoke detector recently being activated or reset. 
     At block  1410 , the device may monitor for smoke in the first mode. In some embodiments, monitoring for smoke in the first mode occurs as detailed in relation to method  1500  of  FIG. 15 —that is only one EM emitter is periodically activated for detecting whether smoke is present in the smoke chamber while at least one other EM emitter is kept disabled (except, possibly, for periodic testing). For instance, the first mode may involve an infrared emitter being activated to permit sampling once every ten seconds. The other emitter(s) may remain disabled, besides for a periodic test. In other embodiments, monitoring for smoke in the first mode occurs as detailed in relation to method  1600  of  FIG. 16 —that is, at least two EM emitters are alternatingly used for assessing an amount of smoke in the smoke chamber with a period of time being waited between illumination with all EM emitters disabled. For instance, both infrared and blue emitters and an EM sensor may be activated to allow for sampling of each to occur once every ten seconds or some other time period. The amount of time between the red and blue emitters being enabled may be a time such as 12.45 msecs. Other times may also be possible, such as between 5 msecs and 1 second, depending on the characteristics of the emitters and sensor. 
     At block  1415 , the mode of the smoke detector may be determined. This determination may be performed in the same manner as detailed at block  1330  of  FIG. 13 . At block  1415 , the Metric Threshold  value used may be 0.04. Therefore, if Metric is greater than 0.04, the second mode may be entered. Based on information gathered while monitoring for smoke at block  1410 , a determination may be made as to whether the smoke detector should remain in the first mode (and return to block  1410  for additional monitoring) or the mode of the smoke detector should be set to the second mode (or directly jumping to the third mode) at block  1415 . Therefore, based on information gathered at block  1410  while monitoring for smoke, the mode of the smoke detector at block  1415  will either be maintained by remaining in the first mode and returning to block  1410  or will be modified to the second (or, possibly, third) mode and method  1400  will proceed to block  1420 . As previously detailed, at block  1415 , the metric value may be calculated and used for determining the mode of the smoke detector, either by direct comparison to a threshold value or by comparing the number of times that the metric value exceeds a threshold value during a sliding window to one or more threshold percentages for a warning or alarm level. In some embodiments, the defined threshold metric value may be 0.15 to determine if the second mode should be entered. 
     At block  1420 , the smoke detector may be set to a second mode. Setting the smoke detector device to a second mode may take the form of a processing system of the smoke detector storing an indication to memory indicative of the second mode being active. The processing system may control the multiple EM emitters and EM sensor in accordance with a sensing definition of the second mode, as defined below. 
     At block  1425 , the device may monitor for smoke in the second mode. In some embodiments, monitoring for smoke in the second mode occurs as detailed in relation to method  1600  of  FIG. 16 —that is, at least two EM emitters are alternatingly used for assessing an amount of smoke in the smoke chamber with a period of time being waited between illumination with all EM emitters disabled. The second mode may be assigned a defined wait period of time, which may indicate an amount of time that is waited between the EM emitters being intermittently activated. 
     At block  1430 , the mode of the smoke detector may be determined. This determination may be performed in the same manner as previously detailed at block  1330  of  FIG. 13 . Based on information gathered while monitoring for smoke at block  1425 , a determination may be made as to whether the smoke detector should remain in the second mode (and return to block  1425  for additional monitoring) or the mode of the smoke detector should be set to the third mode or the first mode. Therefore, based on information gathered at block  1425  while monitoring for smoke, the mode of the smoke detector at block  1430  will either be maintained by remaining in the second mode and returning to block  1410  for the first mode, or will be set to the third mode and method  1400  will proceed to block  1435 . As previously detailed, at block  1430 , the metric value may be calculated and used for determining the mode of the smoke detector, either by direct comparison to a threshold value or by comparing the number of times that the metric value exceeds a threshold value during a sliding window to one or more threshold percentages for a warning or alarm level. In some embodiments, if Metric is less than a threshold of 0.04, the first mode may be entered, if Metric is between thresholds of 0.04 and 0.1, the second mode may remain being used, and if Metric is greater than a threshold of 0.1, the third mode may be entered. It should be understood that the various values for such thresholds are merely exemplary. 
     At block  1435 , the smoke detector may be set to a third mode. Setting the smoke detector device to the third mode may include the processing system of the smoke detector storing an indication to memory indicative of the second mode being active. The processing system may control the multiple EM emitters and EM sensor in accordance with a sensing definition of the second mode, as defined below. For instance, in the third mode both infrared and blue emitters may be activated to allow for sampling of each once every two seconds or some other time period. The amount of time between the red and blue emitters being enabled may be a time such as 12.45 msecs. Other times are also possible, such as between 5 msecs and 1 second, depending on the characteristics of the emitters and sensor. The time period of the third mode can be expected to be less than the time period of the second mode. 
     At block  1440 , the device may monitor for smoke in accordance with the third mode. In some embodiments, monitoring for smoke in the third mode occurs as detailed in relation to method  1600  of  FIG. 16 —that is, at least two EM emitters are alternatingly used for assessing an amount of smoke in the smoke chamber with a period of time being waited between illumination with all EM emitters disabled. The third mode may include a defined wait period of time, which may indicate an amount of time that is waited between the EM emitters being intermittently activated. The defined wait period of time for the third mode may be shorter in duration than the defined period of time for this second mode. 
     At block  1445 , the mode of the smoke detector may again be determined. This determination may be performed in the same manner as previously detailed at block  1330  of  FIG. 13 . Based on information gathered while monitoring for smoke at block  1440 , a determination may be made as to whether the smoke detector should remain in the third mode (and return to block  1440  for additional monitoring) or the mode of the smoke detector should be set to the second mode or the first mode. Therefore, based on information gathered at block  1440  while monitoring for smoke, the mode of the smoke detector at block  1445  will either be maintained by remaining in the third mode, return to block  1410  for the first mode, or be set to the second mode at block  1420 . As previously detailed, at block  1430 , the Metric value may be calculated and used for determining the mode of the smoke detector, either by direct comparison to one or more threshold values or by comparing the number of times that the metric value exceeds one or more threshold values during a sliding window as compared to one or more threshold percentage values for warning or alarm levels. In some embodiments, if Metric is less than a threshold of 0.04, the first mode may be entered, if Metric is between thresholds of 0.04 and 0.1, the second mode may be used, and if Metric is greater than a threshold of 0.1, the third mode may be used. 
     The smoke detector device that performs method  1400  may be configured to output a warning (an indication that a smoke level is rising but has not yet triggered an alarm) and an alarm. The third mode (which results in the fastest rate of sampling) may be triggered at a lower smoke level than the warning level. Therefore, by the time the smoke detector device outputs an auditory warning of an increasing smoke level, the smoke detector device may have already moved from the first mode, to the second mode, and then to the third mode due to the detected level of smoke. Rolling windows, as previously detailed, may be used to determine whether a warning or an alarm should be output based on the Metric value. 
     It should be noted that, throughout this document, reference is made to “first” and “second” modes. Reference is also made to “first” and “second” emitters. These designators are not meant to confer any necessary order or sequence to use of the modes and/or emitters. Rather, these numerical designators are merely intended for clarity as to which mode or emitter the document is currently referring. 
       FIG. 15  illustrates an embodiment of a method  1500  for performing a mode for detecting smoke in a smoke chamber. For example, method  1500  may be used as the first mode in methods  1300  and/or  1400 . As mentioned in relation to  FIGS. 13 and 14 , while the following description focuses on enabling and disabling EM emitters, it should be understood that an EM sensor&#39;s enablement pattern may mirror the EM emitters such that an EM sensor is only powered when an EM emitter is illuminated. In other embodiments, the EM sensor may remain continuously powered and activated. In still other embodiments, the EM sensor may be enabled for longer in duration than the EM emitters, but may still be disabled on a periodic basis to save power and/or prolong the life of the EM sensor. Typically, method  1500  corresponds to a situation where no or very little smoke has been detected by the smoke detector. Of the various modes detailed in this document, method  1500  can result in the least amount of power being consumed and/or EM emitters being, in total, illuminated for the least amount of time (thereby prolonging their collective functional lives). 
     At block  1505 , a first EM emitter is activated. In some embodiments, the first EM emitter is an infrared EM emitter. An infrared EM emitter may be used as the first EM emitter because infrared EM emitters may tend to have a longer lifespan than at least some other types of EM emitters, such as blue light EM emitters. The first EM emitter may be activated for a defined period of time. During this period of time, each other EM emitter present in the smoke chamber is disabled such that the first EM emitter is the only EM emitter outputting EM radiation. During this period of time when the first EM emitter is active at block  1505 , an EM sensor may make a measurement as to an amount of EM radiation sensed at block  1510 . Since the measurement occurs within a smoke chamber designed to eliminate or nearly eliminate the presence of light from the external environment, any light sensed by the EM sensor would most likely be generated by the first EM emitter and, if a significant amount of EM radiation is detected, would have been scattered by particulate matter present within the smoke chamber. 
     At block  1515 , it may be evaluated whether the mode of the smoke detector has changed. This evaluation may represent one of the previous decision blocks, such as block  1330 , where the mode of the smoke detector is reevaluated while the first mode is currently active. If the mode is determined to have changed, based on the measurements sensed at block  1510 , the first mode may be changed to some other mode (such as a second or third mode detailed in relation to  FIG. 16 ). If the determination at block  1515  results in the first mode being maintained, method  1500  may proceed to block  1520 . At block  1520 , a period of time may be waited during which all EM emitters are disabled. This period of time may be 1985 milliseconds (msecs) in duration when a two second sampling rate is in effect. Of course, in other embodiments, this period of time may be longer of shorter, such as any value between 1000 msecs and 3000 msecs. 
     Following block  1520 , method  1500  may return to block  1505 . To be clear, the second EM emitter of the device may not be activated for smoke detection in method  1500 . Therefore, if method  1500  is used for an extended period of time (which may be typical if smoke is very infrequently determined to be present at block  1515 ), the second (and/or third) EM emitter may not be used for smoke detection very often. While the second EM emitter may not be used for smoke detection in method  1500 , periodically, the device performing method  1500  may perform a test of a second EM emitter. For example, during block  1520 , the second EM emitter may be occasionally activated. For instance, in some embodiments, the second EM emitter, which may emit blue light, may be activated once every 200 seconds. In other embodiments, the test period may be other than 200 seconds; for instance, the test period may be any time between 5 and 5000 seconds. If the second EM emitter is functioning properly, the EM sensor may be able to detect a small amount of EM radiation within the smoke chamber, even if no particulate matter is present to deflect the EM radiation emitted by the second EM emitter. That is, the smoke chamber itself may cause a small amount of EM radiation from the active second EM emitter to be deflected/reflected into the EM sensor. If, during this test, at least a test threshold amount of EM radiation is determined to have been sensed by the EM sensor, the second EM emitter is assumed to be functioning properly. While method  1500  does not use the second EM emitter for sensing smoke, method  1500  permits such a periodic test of the second EM emitter to ensure proper functionality. 
     A similar test may be performed for the first EM emitter as part of block  1510 . Since the first EM emitter is periodically active during method  1500 , the smoke chamber itself may cause a small amount of EM radiation from the active first EM emitter to be deflected/reflected into the EM sensor. If, during block  1510 , at least a test threshold amount of EM radiation is determined to have been sensed by the EM sensor, the first EM emitter is assumed to be functioning properly. Different test thresholds may be used for each EM emitter, depending on the wavelength of output EM radiation. Therefore, a different test threshold may be used for blue light as compared to infrared EM radiation. 
       FIG. 16  illustrates an embodiment of a method  1600  for performing a mode for detecting smoke within a smoke chamber. For example, method  1500  may be used as the first and second mode in method  1300 , just the second mode in method  1300 , all of the modes in method  1400 , or the second two modes of method  1400 . As mentioned in relation to  FIGS. 13-15 , while the following description focuses on enabling and disabling EM emitters, it should be understood that an EM sensor&#39;s enablement pattern may mirror the EM emitters such that an EM sensor is only powered when an EM emitter is illuminated. In other embodiments, the EM sensor may remain continuously powered and activated. In still other embodiments, the EM sensor may be enabled for longer in duration than the EM emitters, but may still be disabled on a periodic basis to save power and/or prolong the life of the EM sensor. 
     Method  1600  can be used in the form of multiple modes by varying the period of time at block  1635 . For instance, if method  1600  is used as both modes in method  1300 , for the first mode, method  1600  may have a wait time at blocks  1615  and/or  1635  that is double or triple the wait time used in the second mode version of method  1600 . As such, a large number of modes can be created using method  1600  simply by varying the wait time of blocks  1615  and/or  1635 . 
     At block  1605 , a first EM emitter is activated. In some embodiments, the first EM emitter is an infrared EM emitter; in others, it is a blue light emitter. The first EM emitter may be activated for a defined period of time. During this period of time, each other EM emitter present in the smoke chamber is disabled such that the first EM emitter is the only EM emitter outputting EM radiation. During this period of time when the first EM emitter is active at block  1605 , an EM sensor may make a measurement as to an amount of EM radiation sensed at block  1610 . Since the measurement occurs within a smoke chamber designed to eliminate or nearly eliminate the presence of light from the external environment, any light sensed by the EM sensor would most likely be generated by the first EM emitter and, if a significant amount of EM radiation is detected, would have been scattered by particulate matter present within the smoke chamber. 
     At block  1615 , a period of time may be waited during which all EM emitters are disabled. This period of time may be 12.45 msecs in duration. The time period allocated for block  1615  may be required to be long enough to allow a smooth on-to-off transition for the active emitter (e.g., accounting for worst case transients). Other embodiments in which the period of time is longer or shorter in duration may also be possible, such as between 6-20 msecs. depending on the characteristics of the emitter. 
     At block  1620 , the second EM emitter is activated. The second EM emitter may be activated for the same defined period of time as used at block  1605  or a defined period of time specifically assigned to the second EM emitter. During the active period of time for the second EM emitter, each other EM emitter present in the smoke chamber is disabled such that the second EM emitter is the only EM emitter outputting EM radiation. During this period of time when the second EM emitter is active at block  1620 , the EM sensor (which is the same EM sensor as at block  1610 ) may make a measurement as to an amount of EM radiation sensed at block  1625 . Since the measurement occurs within a smoke chamber designed to eliminate or nearly eliminate the presence of light from the external environment, any light sensed by the EM sensor would most likely be generated by the second EM emitter and, if a significant amount of EM radiation is detected, would have been scattered by particulate matter present within the smoke chamber. 
     At block  1630 , it may be evaluated whether the mode of the smoke detector has changed. This evaluation may represent one of the previous decision blocks, such as block  1330 , where the mode of the smoke detector is reevaluated. If the mode is determined to have changed, based on the measurements sensed at blocks  1610  and  1625 , the mode may be changed to some other mode. If the determination at block  1630  results in the first mode being maintained, method  1600  may proceed to block  1635 . 
     At block  1635 , a period of time may be waited during which all EM emitters are disabled. This period of time may be 1985 msecs in duration for a two second sampling rate. More time spent in this block means less frequent emitter activity, leading to savings in power and to increased longevity in the functional lifespan of the EM emitters. Of course, in other embodiments, this period of time may be longer of shorter, such as any value between 1000 msecs and 3000 msecs. 
     Following block  1635 , method  1600  may return to block  1605 . Since method  1600  involves both EM emitters being activated, a dedicated test step for either of the EM emitters is not necessary. Rather, as previously detailed, during one of the sensing blocks (i.e., blocks  1610  and  1625 ), it may be determined whether at least a minimum threshold amount of EM radiation is sensed (even when no particulate matter is present in the smoke chamber) due to internal reflection characteristics of the smoke chamber. If at least a minimum threshold amount of EM radiation is sensed, it may be assumed that the associated EM emitter is functioning properly. This minimum threshold amount is based on the wavelength of EM radiation emitted by the EM emitter and/or other characteristics of the EM emitter (e.g., field of projection of EM radiation). 
     As detailed in relation to method  1600 , multiple different modes can be created by varying the defined period of time used for waiting at blocks  1615  and  1635 . Similarly, method  1500  of  FIG. 15  can be used to create multiple modes by varying the defined period of time used for waiting at block  1520 . For example, referring to  FIG. 14 , the first mode may correspond to method  1600  using a first, longer defined period of time for block  1520  and the second mode may correspond to method  1600  using a second, shorter defined period of time for block  1520 . 
       FIG. 17  illustrates an embodiment of a system  1700  that may perform various methods of detecting smoke. System  1700  represents a simplified diagram of a system that may be present in a smoke detector device, such as the smoke detectors of  FIGS. 1-2C . It should be understood that various other embodiments of system  1700  may include more than two EM emitters and/or may use more than one EM sensor. 
     System  1700  may include: smoke chamber  1701 , first EM emitter  1710 , second EM emitter  1720 , and EM sensor  1730 . Smoke chamber  1701  can represent any of the various embodiments of a smoke chamber discussed in relation to  FIGS. 2C - FIG. 12 . Other embodiments of smoke chambers may also be used as part of system  1700 . First EM emitter  1710 , second EM emitter  1720 , and EM sensor  1730  are shown within smoke chamber  1701 —as detailed in relation to  FIG. 2C - FIG. 11 , such components may partially enter smoke chamber  1701  or at least have a field of view that extends into smoke chamber  1701 . First EM emitter  1710 , second EM emitter  1720 , and EM sensor  1730  may communicate with processing system  1740 . 
     Processing system  1740  may control when first EM emitter  1710 , second EM emitter  1720 , and EM sensor  1730  are turned on (enabled) and turned off (disabled). Processing system  1740  may enable and disable EM emitters  1710  and  1720  in accordance with methods  1300 - 1600 . Processing system  1740  may receive voltage measurements from EM sensor  1730  at least when such EM emitters  1710  and  1720  are enabled. 
     Processing system  1740  may include one or more processors, such as processor  1741 , and non-transitory computer-readable memory  1742 . Therefore processing means can involve the use of one or more processors that serve to control first EM emitter  1710 , second EM emitter  1720 , and EM sensor  1730  and can perform methods  1300 - 1600 . Memory  1742  may be used to store instructions that cause processor  1741  (and/or any other processor) to perform blocks of the methods  1300 - 1600 . In some embodiments, processor  1741  may be specialized to perform such methods directly. In some embodiments, firmware can be instantiated on processor  1741  to perform such methods. 
       FIG. 18  illustrates an embodiment of a graph showing the relationship between infrared and blue light measurements by an EM sensor. The instantaneous Metric is compared against these thresholds to assess whether smoke has reached warning or alarm levels. The graph of  FIG. 18  shows a threshold line for an alarm and a threshold line for a “Heads Up” message, which serves as a warning as to rising smoke levels. In  FIG. 18 , ired level  on the x-axis is graphed against blue level . The dotted line indicates where the combination of the measured ired level  and the measured blue level  will trigger a warning. The solid line indicates where the combination of the measured ired level  and the measured blue level  will trigger an alarm. Therefore, when a combination of the measured blue light by the EM sensor and the measured infrared EM radiation by the EM sensor results in a point on the graph to the right of “heads up” but to the left of “alarm”, a positive (true) is input into the warning sliding window. When a sufficient number of positives has been detected within the allotted time span of the warning sliding window, an auditory warning (e.g., recorded or synthesized message, flashing or pulsing light of a particular color, such as yellow) may be output. When a combination of the measured blue light by the EM sensor and the measured infrared EM radiation by the EM sensor results in a point on the graph to the right of “alarm”, a positive (true) is input into the alarm sliding window. When a sufficient number of positives has been detected within the allotted time span of the alarm sliding window, an alarm (e.g., loud buzzer) may be sounded. The calculated value of Metric from equation one can be used to determine if the threshold defined by the dotted line (warning threshold) is exceeded and/or the threshold defined by the solid line (alarm threshold) is exceeded by defining a threshold value for comparison with Metric and defining the scaling factors of equation 1. Therefore, the threshold lines of  FIG. 18  can be defined by setting a threshold value for Metric and selecting particular scaling factors for ired scaling  and blue scaling . 
       FIG. 19  illustrates an embodiment of the graph of  FIG. 18  showing data points from two separate foam block fires. The various data points presented were gathered over time. As can be seen, the two fires have roughly the same properties early during the fire, but a first fire (associated with data points  1901 ) caused a relative greater amount of deflected blue light to be detected, while a second fire (associated with data points  1902 ) caused a relative greater amount of deflected infrared light to be detected. When the value of ired level  and blue level  exceed the “headsup” threshold, a warning may be sounded and when the value of ired level  and blue level  exceed the “alarm” threshold, an alarm may be sounded by the device. 
       FIG. 20  illustrates an embodiment of the graph of  FIG. 19  showing data points from the two foam block fires in three dimensions against time. It can be seen how as time increases, the characteristics of the fires varied. Such variance may be due at least in part to differences in environment (e.g., temperature, humidity) and air flow conditions due to the units locations with respect to the fire source and to the inherent randomness in the smoke behavior. 
     A computer system as illustrated in  FIG. 21  may be incorporated as part of the previously described computerized devices, such as the processing system of  FIG. 17  or on-board the device of  FIG. 2C .  FIG. 21  provides a schematic illustration of one embodiment of a computer system  2100  that can perform various steps of the methods provided by various embodiments. It should be noted that  FIG. 21  is meant only to provide a generalized illustration of various components, any or all of which may be utilized as appropriate.  FIG. 21 , therefore, broadly illustrates how individual system elements may be implemented in a relatively separated or relatively more integrated manner. 
     The computer system  2100  is shown comprising hardware elements that can be electrically coupled via a bus  2105  (or may otherwise be in communication, as appropriate). The hardware elements may include one or more processors  2110 , including without limitation one or more general-purpose processors and/or one or more special-purpose processors (such as digital signal processing chips, graphics acceleration processors, video decoders, and/or the like); one or more input devices  2115 , which can include without limitation a mouse, a keyboard, remote control, and/or the like; and one or more output devices  2120 , which can include without limitation a display device, a printer, and/or the like. 
     The computer system  2100  may further include (and/or be in communication with) one or more non-transitory storage devices  2125 , which can comprise, without limitation, local and/or network accessible storage, and/or can include, without limitation, a disk drive, a drive array, an optical storage device, a solid-state storage device, such as a random access memory (“RAM”), and/or a read-only memory (“ROM”), which can be programmable, flash-updateable and/or the like. Such storage devices may be configured to implement any appropriate data stores, including without limitation, various file systems, database structures, and/or the like. 
     The computer system  2100  might also include a communications subsystem  2130 , which can include without limitation a modem, a network card (wireless or wired), an infrared communication device, a wireless communication device, and/or a chipset (such as a Bluetooth™ device, an 802.11 device, a WiFi device, a WiMax device, cellular communication device, etc.), and/or the like. The communications subsystem  2130  may permit data to be exchanged with a network (such as the network described below, to name one example), other computer systems, and/or any other devices described herein. In many embodiments, the computer system  2100  will further comprise a working memory  2135 , which can include a RAM or ROM device, as described above. 
     The computer system  2100  also can comprise software elements, shown as being currently located within the working memory  2135 , including an operating system  2140 , device drivers, executable libraries, and/or other code, such as one or more application programs  2145 , which may comprise computer programs provided by various embodiments, and/or may be designed to implement methods, and/or configure systems, provided by other embodiments, as described herein. Merely by way of example, one or more procedures described with respect to the method(s) discussed above might be implemented as code and/or instructions executable by a computer (and/or a processor within a computer); in an aspect, then, such code and/or instructions can be used to configure and/or adapt a general purpose computer (or other device) to perform one or more operations in accordance with the described methods. 
     A set of these instructions and/or code might be stored on a non-transitory computer-readable storage medium, such as the non-transitory storage device(s)  2125  described above. In some cases, the storage medium might be incorporated within a computer system, such as computer system  2100 . In other embodiments, the storage medium might be separate from a computer system (e.g., a removable medium, such as a compact disc), and/or provided in an installation package, such that the storage medium can be used to program, configure, and/or adapt a general purpose computer with the instructions/code stored thereon. These instructions might take the form of executable code, which is executable by the computer system  2100  and/or might take the form of source and/or installable code, which, upon compilation and/or installation on the computer system  2100  (e.g., using any of a variety of generally available compilers, installation programs, compression/decompression utilities, etc.), then takes the form of executable code. 
     It will be apparent to those skilled in the art that substantial variations may be made in accordance with specific requirements. For example, customized hardware might also be used, and/or particular elements might be implemented in hardware, software (including portable software, such as applets, etc.), or both. Further, connection to other computing devices such as network input/output devices may be employed. 
     As mentioned above, in one aspect, some embodiments may employ a computer system (such as the computer system  2100 ) to perform methods in accordance with various embodiments of the invention. According to a set of embodiments, some or all of the procedures of such methods are performed by the computer system  2100  in response to processor  2110  executing one or more sequences of one or more instructions (which might be incorporated into the operating system  2140  and/or other code, such as an application program  2145 ) contained in the working memory  2135 . Such instructions may be read into the working memory  2135  from another computer-readable medium, such as one or more of the non-transitory storage device(s)  2125 . Merely by way of example, execution of the sequences of instructions contained in the working memory  2135  might cause the processor(s)  2110  to perform one or more procedures of the methods described herein. 
     The terms “machine-readable medium,” “computer-readable storage medium” and “computer-readable medium,” as used herein, refer to any medium that participates in providing data that causes a machine to operate in a specific fashion. These mediums may be non-transitory. In an embodiment implemented using the computer system  2100 , various computer-readable media might be involved in providing instructions/code to processor(s)  2110  for execution and/or might be used to store and/or carry such instructions/code. In many implementations, a computer-readable medium is a physical and/or tangible storage medium. Such a medium may take the form of a non-volatile media or volatile media. Non-volatile media include, for example, optical and/or magnetic disks, such as the non-transitory storage device(s)  2125 . Volatile media include, without limitation, dynamic memory, such as the working memory  2135 . 
     Common forms of physical and/or tangible computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, any other physical medium with patterns of marks, a RAM, a PROM, EPROM, a FLASH-EPROM, any other memory chip or cartridge, or any other medium from which a computer can read instructions and/or code. 
     Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to the processor(s)  2110  for execution. Merely by way of example, the instructions may initially be carried on a magnetic disk and/or optical disc of a remote computer. A remote computer might load the instructions into its dynamic memory and send the instructions as signals over a transmission medium to be received and/or executed by the computer system  2100 . 
     The communications subsystem  2130  (and/or components thereof) generally will receive signals, and the bus  2105  then might carry the signals (and/or the data, instructions, etc. carried by the signals) to the working memory  2135 , from which the processor(s)  2110  retrieves and executes the instructions. The instructions received by the working memory  2135  may optionally be stored on a non-transitory storage device  2125  either before or after execution by the processor(s)  2110 . 
     It should further be understood that the components of computer system  2100  can be distributed across a network. For example, some processing may be performed in one location using a first processor while other processing may be performed by another processor remote from the first processor. Other components of computer system  2100  may be similarly distributed. As such, computer system  2100  may be interpreted as a distributed computing system that performs processing in multiple locations. In some instances, computer system  2100  may be interpreted as a single computing device, such as a distinct laptop, desktop computer, or the like, depending on the context. 
     The methods, systems, and devices discussed above are examples. Various configurations may omit, substitute, or add various procedures or components as appropriate. For instance, in alternative configurations, the methods may be performed in an order different from that described, and/or various stages may be added, omitted, and/or combined. Also, features described with respect to certain configurations may be combined in various other configurations. Different aspects and elements of the configurations may be combined in a similar manner. Also, technology evolves and, thus, many of the elements are examples and do not limit the scope of the disclosure or claims. 
     Specific details are given in the description to provide a thorough understanding of example configurations (including implementations). However, configurations may be practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques have been shown without unnecessary detail in order to avoid obscuring the configurations. This description provides example configurations only, and does not limit the scope, applicability, or configurations of the claims. Rather, the preceding description of the configurations will provide those skilled in the art with an enabling description for implementing described techniques. Various changes may be made in the function and arrangement of elements without departing from the spirit or scope of the disclosure. 
     Also, configurations may be described as a process which is depicted as a flow diagram or block diagram. Although each may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be rearranged. A process may have additional steps not included in the figure. Furthermore, examples of the methods may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware, or microcode, the program code or code segments to perform the necessary tasks may be stored in a non-transitory computer-readable medium such as a storage medium. Processors may perform the described tasks. 
     Having described several example configurations, various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. For example, the above elements may be components of a larger system, wherein other rules may take precedence over or otherwise modify the application of the invention. Also, a number of steps may be undertaken before, during, or after the above elements are considered.