Abstract:
A system and method are disclosed for alerting safety personnel of unsafe air temperature conditions. The system includes a temperature sensor exposed to the ambient environment, a temperature indicator disposed in a field of view of safety gear such as a face mask, and a control unit. The temperature indicator and the control unit may be disposed in a protected location, such as within the face mask. The control unit may produce warnings based on detected temperatures and exposure time thresholds. Detected temperatures may also be recorded, along with positioning information, such as GPS data, to facilitate mapping of temperature gradients. At startup, the system may automatically execute a battery check and produce a warning if insufficient charge remains to provide a predetermined operating time. Various embodiments may use an arm to keep the temperature indicator within the field of view or a single screw attachment to a face piece.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation application of U.S. patent application Ser. No. 09/595,321 filed Jun. 16, 2000 entitled SYSTEM AND METHOD FOR IDENTIFYING UNSAFE TEMPERATURE CONDITIONS, now U.S. Pat. No. ______, which is a continuation-in-part of U.S. application Ser. No. 09/182,823, filed Oct. 29, 1998 entitled, SYSTEM AND METHOD FOR ALERTING SAFETY PERSONNEL OF UNSAFE AIR TEMPERATURE CONDITIONS, now U.S. Pat. No. 6,118,382 which claims priority to provisional application number 60/064,324, filed Oct. 30, 1997. 
     
    
     
       TECHNICAL FIELD OF THE INVENTION  
         [0002]    The present invention relates in general to the field of equipment for firefighters and other safety personnel, and, more particularly, to a system and method for alerting safety personnel of unsafe air temperature conditions.  
         BACKGROUND OF THE INVENTION  
         [0003]    Firefighters and other safety personnel use various types of equipment when fighting a fire. This equipment typically includes a coat, boots, gloves and other clothing specially created to protect against fire and heat as well as a self contained breathing apparatus to provide oxygen. Although such equipment provides some protection, firefighter&#39;s still face significant dangers including the danger of a flashover. In general, once the ambient temperature in a fire reaches about 600 degrees Fahrenheit, the temperature will quickly rise to over 1100 degrees Fahrenheit. At this point, a flashover can occur in which the air ignites and kills or severely injures firefighters. Thus, it is unsafe to fight fires once the ambient temperature reaches around 600 degrees Fahrenheit.  
           [0004]    To alleviate some of the dangers involved in firefighting, various electronic devices have been developed to provide warnings to firefighters. For example, U.S. Pat. No. 5,640,148 discloses a dual activation alarm system for a personal alert safety system (PASS). U.S. Pat. No. 5,635,909 discloses a temperature monitoring assembly that is incorporated into a garment such as a coat. This device includes a speaker to provide an audible alarm. U.S. Pat. No. 5,541,549 discloses a personal alarm safety system that is designed as part of the firefighter&#39;s belt. Further, U.S. Pat. No. 5,137,378 discloses an integrated firefighter safety monitoring and alarm system that provides a number of warnings to a firefighter. This system includes temperature monitoring and provides an audible alarm. The system also has a display for providing additional information to the firefighter including a visible warning. The system is contained in a case that can have a belt or mounting clip for attaching to the firefighter&#39;s equipment.  
           [0005]    However, even with such conventional devices, firefighters are still injured or killed by flashovers. The complexity of the conventional devices, the difficulties of the firefighting environment and the type and location of the warnings cause firefighters not to hear audible warnings or not to see visible warnings of dangerous ambient temperatures.  
         SUMMARY OF THE INVENTION  
         [0006]    In accordance with the present invention, a system and method for alerting safety personnel of unsafe air temperature conditions are disclosed that provide advantages over previously developed temperature warning equipment.  
           [0007]    According to one aspect of the present invention, a system for alerting safety personnel of ambient air temperature conditions is provided. The system includes a control unit stored within a housing wherein the control unit includes electronics operable to communicate a signal associated with an ambient air temperature condition. The system also includes a sensor unit communicatively coupled to the control unit wherein the sensor unit operable to be positioned within an ambient environment at a distance from the control unit. The sensor unit includes a temperature sensor operable to sense an ambient air temperature and an indicator operable to provide an indication representing the ambient air temperature condition.  
           [0008]    According to another aspect of the present invention, a method for operating a safety device for displaying ambient air temperature conditions to safety personnel is provided. The method includes sensing an ambient air temperature using a temperature sensing device and determining a mode of operation associated with the device in response to the sensed temperature.  
           [0009]    According to a further aspect of the present invention, a removable safety system operable to be coupled to safety personnel for detecting ambient temperature conditions is provided. The system includes a control unit operable to be coupled to the safety personnel having electronics operable to communicate signals associated with the ambient air condition. The system further includes a sensor unit operable to be positioned with an ambient environment and coupled to a substantially centered position of a viewmask. The sensor unit includes a temperature sensor having an temperature dependent operating mode communicatively coupled to the control unit and a first indicator and second indicator operable to display an indication representing an ambient air temperature condition.  
           [0010]    A technical advantage of the present invention is the providing of indicators and/or alarms to safety personnel focused upon the personal safety of the firefighter. The trigger points, rather than being focused on equipment safety, focus upon the safety personnel.  
           [0011]    Another technical advantage of the present invention is the ease of use in that the temperature indicators are positioned within the personnel&#39;s peripheral vision near the face mask of a self contained breathing apparatus. The present invention can help save lives by providing a passively visible warning that the environment is approaching flashover conditions. Further, the present invention may save on taxpayer&#39;s funds that would have otherwise been spent on fire suit replacements, compensation packages and downtime costs.  
           [0012]    A further technical advantage of the present invention is providing a system having an operating mode dependent on an ambient air temperature conditions and system operating availability.  
           [0013]    Another technical advantage of the present invention is providing a removable safety system which may be coupled to conventional firefighting equipment such as face shields, helmets, mask webbings and the like.  
           [0014]    Additional technical advantages should be readily apparent from the drawings, description, and claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    A more complete understanding of the present invention and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings in which like reference numbers indicate like features and wherein:  
         [0016]    [0016]FIG. 1 is a block diagram of one embodiment of a system for alerting safety personnel of unsafe air temperature conditions according to the present invention;  
         [0017]    [0017]FIG. 2 is a flow chart of one embodiment of a method for alerting safety personnel of unsafe air temperature conditions according to the present invention;  
         [0018]    [0018]FIG. 3 is a perspective view of one embodiment of a system for alerting safety personnel of unsafe air temperature conditions constructed according to the present invention; and  
         [0019]    [0019]FIG. 4 is a perspective view of one embodiment of the system of FIG. 3 coupled to a self contained breathing apparatus face piece according to the present invention;  
         [0020]    [0020]FIG. 5 is a block diagram of another embodiment of a system for alerting safety personnel of unsafe air temperature conditions;  
         [0021]    [0021]FIGS. 6A, 6B,  6 C,  6 D and  6 E are diagrams of one embodiment of a through-screw sensor assembly for a system for alerting safety personnel of unsafe air temperature conditions constructed according to the present invention;  
         [0022]    [0022]FIG. 7 illustrates a system for alerting safety personnel of unsafe air temperature conditions according to another embodiment present invention;  
         [0023]    [0023]FIG. 8 is a rear perspective view of the sensor assembly illustrated in FIG. 7 according to the present invention;  
         [0024]    [0024]FIG. 9 is a lateral perspective view of the system of FIG. 7 coupled to a self contained breathing apparatus face piece according to one embodiment of the present invention;  
         [0025]    [0025]FIG. 10A is a front perspective view of the system of FIG. 7 coupled to a self contained breathing apparatus face piece according to one embodiment of the present invention;  
         [0026]    [0026]FIG. 10B is a lateral perspective view of the system of FIG. 7 coupled to a self contained breathing apparatus face piece according to one embodiment of the present invention;  
         [0027]    [0027]FIG. 10C is a top perspective view of the system of FIG. 7 coupled to a self contained breathing apparatus face piece according to one embodiment of the present invention;  
         [0028]    [0028]FIG. 11 is a flow chart of a method for alerting safety personnel of unsafe air temperature conditions according to another embodiment of the present invention;  
         [0029]    [0029]FIG. 12 is a flow chart of a method for activating a safety device for alerting safety personnel of unsafe air temperature conditions according to one embodiment of the present invention; and  
         [0030]    [0030]FIG. 13 is a block diagram of a system for alerting safety personnel of unsafe air temperature conditions according to another embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    [0031]FIG. 1 is a block diagram of one embodiment of a system, indicated generally at  10 , for alerting safety personnel of unsafe air temperature conditions according to the present invention. As shown, system  10  has a microprocessor  12  that receives power from a battery  14 . Microprocessor  12  serves as a control unit for system  10 , which control unit, it should be understood, could comprise other types of control devices. Battery  14  can be replaced by the user and can be conserved by switching system  10  off when not in use. System  10  also includes a low battery voltage detect circuit  16  and can be turned on and off by an on/off switch  18  and test push-button  18 . This switch  18  can be backed up by an automatic switch (not shown) that turns system  10  on when the ambient temperature reaches a certain point, such as is 150 degrees Fahrenheit.  
         [0032]    A temperature sensor  22  measures temperature and provides an output to a comparator circuit  24  which has digital potentiometers for adjustable indicator set points. Temperature sensor  22  can, for example, be a resistive temperature device (RTD), thermocouple, thermistor or infra-red (IR) sensor. In the embodiment of FIG. 1, system  10  has dual thresholds, but it should be understood that more thresholds could be implemented if appropriate. Also, in the embodiment of FIG. 1, digital potentiometers can be set by signals from microprocessor  12 .  
         [0033]    In operation, comparator circuit  24  provides a signal to microprocessor  12  in response to a comparison between the digital potentiometers and the output from temperature sensor  22 . Microprocessor  12  then provides signals to drive two visible indicators  28 , as shown. These visible indicators  28  can, for example, be LED, LCD, heads-up-display, fiber optic or incandescent indicators. In the illustrated embodiment, visible indicators  28  indicate an ambient temperature of 300 degrees Fahrenheit and 600 degrees Fahrenheit, respectively. However, these settings are variable and could be other values. Further microprocessor  12  can provide signals to an optional alarm  30 . The alarm can, for example, be an audible or vibration alarm.  
         [0034]    The microprocessor control of system  10  can provide additional enhancements to temperature monitoring for the safety of safety personnel. For example, system  10  can utilize time averaged measurements for additional or alternate indicators. Such time averaged measurements identify the fact that the safety personnel has been at a given ambient temperature for a given amount of time. Examples of time averaged measurements include: 160 degrees Fahrenheit for 60 seconds, 180 degrees Fahrenheit for 30 seconds, 212 degrees Fahrenheit for 15 seconds, and 500 degrees Fahrenheit for 60 seconds. System  10  can react to such events by providing additional visible indicators and alarms. Another enhanced feature is an ability to record and provide a temperature history for a post-event analysis. For example, the temperature could be recorded at specified intervals of time while the firefighter or other safety personnel is working to give an idea of the temperature profile within the site. Further, this could be linked with positioning information, such as from GPS equipment, to “map” the temperature gradients within the site. The recording can, for example, be into on-board random access memory.  
         [0035]    One purpose of system  10  is to provide firefighter and other safety personnel with an early warning of excessive temperatures that would eventually lead to a flashover or other danger. In general, once the ambient temperature in a fire reaches 300 degrees Fahrenheit, the temperature will start rising, and it takes around 2 minutes, linearly, to reach 600 degrees Fahrenheit. Once the temperature reaches that threshold, the temperature will start rising exponentially to over 1100 degrees Fahrenheit in less than a minute. This fatal phenomenon is termed a flashover. It is appropriate to evacuate buildings or other structures once the temperature reaches around 600 degrees Fahrenheit. Further, other temperature related conditions can be unsafe for firefighters. For example, as mentioned above, remaining in a high ambient temperature for a certain period of time can be dangerous.  
         [0036]    In one implementation, the present invention provides a system that generally incorporates a remote temperature sensing device encapsulated with batteries and indicators (e.g., green and red indicators such as miniature incandescent lights) within an insulated enclosure which is mounted within the peripheral vision of the self-contained breathing apparatus (SCBA) that firefighters wear. The green and red indicators will glow the moment the ambient temperature rises above 300 degrees Fahrenheit or 600 degrees Fahrenheit, respectively. This early signaling will afford firefighters with ample time to react to the situation and make informed decisions as to whether to proceed or revert. Not only will the present invention save many firefighter&#39;s lives, but, in turn, will also save on taxpayer&#39;s funds that would have otherwise been spent on fire suit replacements, firefighter&#39;s compensation packages and downtime costs.  
         [0037]    [0037]FIG. 2 is a flow chart of one embodiment of a method for alerting safety personnel of unsafe air temperature conditions according to the present invention. As shown, in step  40 , the start switch is activated. This activation can be manual or automatic as mentioned above. Then, in step  41 , the system begins an internal self test. In step  42 , the system checks whether the battery is low. If so, in step  43 , the system flashes one of the indicators to signal the problem. In step  44 , the system determines whether the self-test failed. If so, in step  45 , the system flashes the other indicator to signal this failure. If the tests do not fail, in step  46 , the system illuminates both indicators for five seconds and beeps the installed speaker (if any).  
         [0038]    In step  48 , the system then allows a user to program the digital potentiometers for the temperature set points. This can be an optional step if the digital potentiometers are already set. Then, in step  50 , the system measures the ambient temperature on an ongoing basis using the temperature sensor. In step  52 , the system determines it is switched off. If so, then the process stops. Otherwise, the system checks, in step  54 , whether the temperature is at the first set point (e.g., 300 degrees Fahrenheit) or greater. If not, then the system returns to measuring the temperature. If the temperature is greater than 300 degrees Fahrenheit, then the system illuminates the first indicator in step  55 . Then, in step  56 , the system checks whether the temperature is greater than the second set point (e.g., 600 degrees Fahrenheit). If not, the system returns to measuring the temperature of step  50 . If the temperature is greater than 600 degrees Fahrenheit, then the system illuminates the second indicator in step  58  and then returns to measure temperature, as shown. In this manner, the system continually monitors the ambient temperature and provides a visible warning of the ambient temperature is above either of the temperature set points. It should be understood that other implementations would include other steps. For example, an implementation having time averaged measurements would involve steps for averaging temperature over a specified interval of time and alerting a firefighter or other safety personnel when certain conditions have been met.  
         [0039]    [0039]FIG. 3 is a perspective view of one embodiment of an system, indicated generally at  60 , for alerting safety personnel of unsafe air temperature conditions constructed according to the present invention. As shown, system  60  comprises electronics  62  that are contained primarily in a housing  64  with the exception of visible indicators  66  and a sensor  68  which are positioned at the end of an arm  70  extending from housing  64 . In this embodiment, sensor  68  and indicators  66  on arm  70  can be exposed to the ambient temperatures, while the remaining portions of system  60  are protected within the firefighters equipment. Further, this allows the sensor  68  and indicators  66  to be easily replaceable with a detachable arm  70 . Electronics  62  can be implemented, for example, according to the block diagram of FIG. 1, above.  
         [0040]    [0040]FIG. 4 is a perspective view of one embodiment of system  60  of FIG. 3 coupled to a self contained breathing apparatus face piece  72  according to the present invention. As shown, housing  64  of system  60  is attached to face piece  72  which is coupled to a firefighter&#39;s helmet. A arm  70  then extends from housing  64  and positions indicators  66  within the peripheral vision of the firefighter. In this manner, the firefighter can passively see indicators  66  without actively having to look away or otherwise take attention away from firefighting tasks.  
         [0041]    According to the present invention, system  60  can be a completely self-contained unit attached to the firefighter&#39;s self-contained breathing apparatus (SCBA) face piece  72 . System  60  operates to alert a firefighter when the ambient temperature has reached an unsafe level, for example, that would lead to a flashover. System  60  can be mounted in a fashion such that indicators  66  (e.g., LEDs, miniature incandescent lights) which turn on at pre-determined temperatures are other defined conditions, lie within the firefighter&#39;s peripheral vision.  
         [0042]    As shown above, a switch can turn system  60  on and also can serve as a daily test button. A successful self-test can illuminate indicators  66 , then turn them off and allow a speaker to beep (if present). If there is a problem with electronics  62 , indicators  38  can flash an error sequence when system  60  is switched on. Also, the power switch can be backed up by an automatic switch that turns system  60  on when the ambient temperature reaches a specified point.  
         [0043]    According to the present invention, visible indicators are placed in the field of view, for example, while a firefighter is fighting a fire. When the ambient temperature reaches a first set point (e.g., 300° F.), the first indicator will be illuminated and will stay on as long as the temperature is at the set point or above. When the ambient temperature reaches the second set point (e.g., 600° F.), the second indicator will illuminate and will stay on as long as the temperature is at that set point or above. The second indicator can indicate that there is a very short time period before temperatures reach a point at which flashover could occur. At this point, the firefighter (or other personnel) should consider immediately leaving the area to avoid a life threatening situation. Since the set points can be predetermined, the first set point can be set at the face piece manufacturer&#39;s suggested temperature rating for the normal functioning of the face piece to serve as an equipment failure warning. As mentioned above, the temperature set points can be varied by reprogramming of the digital potentiometers to provide alerts as to other unsafe conditions.  
         [0044]    [0044]FIG. 5 is a block diagram of another embodiment of a system, indicated generally at  80 , for alerting safety personnel of unsafe air temperature conditions. As can be seen, system  80  is similar to system of FIG. 10 of FIG. 1. In the embodiment of FIG. 5, system  80  has a microprocessor  82  that receives power from a battery and low voltage detection circuit  84 . Microprocessor  82  serves as a control unit for system  80 , which could comprise alternate types of control devices as mentioned above. System  80  can be turned on and off by an on/off switch  86  which also can operate as a test push-button. A temperature sensor  88  measures temperature and provides an output to a comparator circuit or A/D converter  90  of microprocessor  82 . Microprocessor  82  then provides signals to visible indicators  92  which have variable set points for indicating ambient temperature levels (e.g., 140° F. and 400° F.).  
         [0045]    In operation, comparator circuit or A/D converter  90  provides a signal to microprocessor  82  in response to a measurement by temperature sensor  88 . Microprocessor  82  then provides signals to drive visible indicators  92 . Further microprocessor  82  can provide signals to an optional vibration alarm  94  (e.g., mechanical motor, solenoid) and audible alarm  96 . Further, microprocessor  82  comprises a serial port  98  which can output data to an infrared data port  100  for external interface to system  80 . This could be user, for example, to recover a recorded temperature history or other pertinent information.  
         [0046]    [0046]FIGS. 6A, 6B,  6 C,  6 D and  6 E are diagrams of one embodiment of a through-screw sensor assembly for a system for alerting safety personnel of unsafe air temperature conditions constructed according to the present invention. As shown in FIG. 6A, a face mask  110  receives a through-screw sensor assembly, indicated generally at  112 . Assembly  112  includes a pair of visible indicators  114  positioned within the range of vision of personnel wearing face mask  110 . As can be seen, FIG. 6B is a side view of face mask  110 . FIG. 6 also indicates an area shown in more detail in FIG. 6C.  
         [0047]    [0047]FIG. 6C provides a detailed view of assembly  112  affixed to face mask  110 . As shown, assembly  112  comprises a hollow Allen head screw  116  which is coupled to face mask  110 . Assembly  112  further comprises a nut  118  positioned outside a front portion  120  of face mask  110  and a washer  122  position inside front portion  120 . Together, screw  116 , nut  118  and washer  122  removably attach to front portion  120 . Further, these components also hold a circuit board  124  to which indicators  114  are connected. FIG. 6D provides an explosion view of these same components of assembly  112 . In addition, FIG. 6E provides a cross section diagram of screw  116 . As shown, screw  116  has a hollow center  126  which can provide a connection to a resistive temperature device (RTD)  128 .  
         [0048]    [0048]FIG. 7 illustrates a system for alerting safety personnel of unsafe air temperature conditions according to another embodiment of the present invention. The system, illustrated generally at  200 , is an exemplary form of the system illustrated in FIGS. 6A, 6B,  6 C,  6 D and  6 E. System  200 , includes a sensor unit illustrated as sensor assembly  202  having a through-screw aperture  204  and a mounting channel  210  for mounting sensor assembly  202  to a safety personnel&#39;s safety gear such as a safety helmet, face piece or face mask, etc. Sensor assembly  202  further includes a first indicator  206 , a second indicator  207  and a sensor  205  operable to sense temperature conditions within an ambient. In one embodiment, sensor assembly  202  may include waterproofing such as a high-temperature clear silicone plastic potting compound operable to withstand elevated temperatures while limiting exposure to water and other elements which may be encountered in a firefighting environment. Sensor assembly  202  is coupled via a cable  203  to housing  201  which includes a control unit and associated electronics for alerting safety personnel of air temperature conditions. Housing  201  further includes a clip  208  operable to be clipped to a safety personnel&#39;s safety gear such as a helmet, clothing, face mask webbing and the like. In one embodiment, housing  202  may be made of a waterproof material operable to withstand high temperatures while minimizing precipitant exposure of the electronics stored within housing  202 . Housing  202  may include high-temperature silicon-rubber seals such as, for example, Viton ® seals developed Dupont-Dow Elastomers, L.L.C., operable to withstand elevated temperatures while minimizing exposure to water and other elements.  
         [0049]    In one embodiment, sensor  205  may include a thin element operable to be positioned within an opening or cavity associated with sensor  205 . The thin element may include a front surface and a rear surface operable to be placed within an ambient environment. Sensor assembly  202  may include a cavity or opening at or near the tip or end of sensor assembly as illustrated in FIG. 7 and FIG. 8 below. As such, Sensor assembly  202  may provide an air flow path operable to allow ambient air to flow through the cavity and to exposed sensor  205  including the thin element. Sensor  205  may be positioned away from a mask or face shield (not shown) and within an ambient environment such that system  200  may consistently and accurately sense temperatures.  
         [0050]    System  200  advantageously provides a safety alarm system that may be easily coupled or removed from safety equipment for ensuring the safety of personnel. FIG. 8 is a rear perspective view of the sensor assembly illustrated in FIG. 7. Sensor assembly  202  includes a plurality of screws  209  for coupling the front and rear surfaces of sensor assembly  202 . Though not illustrated, front and rear surfaces may be realized as a one-piece molded unit which may not require screws to couple the front and rear surfaces of sensor assembly  202 .  
         [0051]    Through-screw aperture  204  and mounting channel  210  may be operable to mount sensor assembly  202  to a safety personnel&#39;s safety gear. Sensor assembly  202  also includes first indicator  206  and second indicator  207  operable to provide visible indications of temperature conditions detected by system  200 .  
         [0052]    In one embodiment, sensor assembly  202  may include rounded surfaces which may reduce snagging or jarring of sensor assembly  202  during use. Sensor assembly  202  may include a front surface made of a dark material and a rear surface made of an optically transmittable or substantially clear material which may include a microprism high-visibility surface finish to enhance visibility of indicators  206  and  207 . Indicators  206  and  207  may also include optical transmission channels operable to transmit light to the outer surface of indicators  206  and  207  and sensor  205 . In this manner, a user may view indicators  206  and  207  when illuminated, while other personnel proximal to the user may view an illuminated indicator via indicators  206  and  207  having optical transmission channels. For example, indicators  206  and  207  may be visible to other firefighters from the front of sensor assembly  202  by illuminating indicators  206  and  207  which include optical transmission channels or light conducting paths to outer portions of indicators  206  and  207  as illustrated in FIG. 7. As such, both the user and other personnel may view an indication representing a temperature condition.  
         [0053]    During use, system  200  provides an advantageous system for alerting safety personnel of unsafe air temperature conditions. System  200 , having a control unit within housing  201 , includes electronics operable to communicate a signal associated with a detected temperature condition. Cable  203  may be communicatively coupled between sensor assembly  202  and housing  201 . Sensor assembly  202  may be positioned within an ambient. In one embodiment, sensor  205  may be operable as “active” temperature sensor to provide continues monitoring of temperature conditions by sampling an ambient temperature on a periodic basis (e.g. every four seconds, eight records, etc.) . In this manner, a detected ambient temperature condition may then be used to determine if an operating mode of system  200  should be altered. For example, system  200  may be operable to sample an ambient temperature condition every eight seconds and, upon detecting an ambient temperature condition the sample rate of the ambient temperature (e.g. increase sampling from eight seconds to four seconds). As such, system  200  may be operable to continuously monitor ambient temperature conditions while conserving energy of a power source, such as a battery, associated with system  200 .  
         [0054]    System  200  may be operable to provide a user an indication of ambient temperature conditions. For example, first indicator  206 , operable as a green indicator, such as a miniature incandescent light, may be continuously illuminated during a safe temperature condition. Upon system  200  determining an unsafe ambient air temperature condition, control unit  201  may provide a signal to second indicator  206 , operable as a red indicator, such as a miniature incandescent light, in response to a detected unsafe air temperature condition. For example, an unsafe air temperature condition may include sending a temperature of five hundred degrees Fahrenheit. As such, system  200  may be operable to continuously illuminate second indicator  206  operable as a red indicator.  
         [0055]    [0055]FIG. 9 is a lateral perspective view of the system of FIG. 7 coupled to a self contained breathing apparatus face piece according to one embodiment of the present invention. System  200  may be coupled to a face mask  221  of a self contained breathing apparatus  230 . Sensor assembly  202  may be coupled to a front portion of face mask  221  such that a user may view the indicators of sensor assembly  202 . Housing  201  includes self test button  213  for checking the operating status of system  200  and may be operable to perform a battery test, determine a battery life, perform system diagnostics, etc. Housing  201  may be coupled to a face mask webbing  220  using clip  208  such that housing  206  may be covered by a helmet or other safety headgear (not shown). Housing  201  is coupled to sensor assembly  202  via cable  203  which may be positioned behind or along a portion of face mask  221  and face mask webbing  220 . As stated above cable  203 , sensor assembly  202  and housing  201  are preferably made of high quality materials capable of withstanding high temperature levels for extended periods of time (e.g. greater than five hundred degrees Fahrenheit for several minutes). System  200  advantageously allows for a user to position system  200  such that, during use, system  200  may be comfortably worn in addition to being easy to couple or remove as required. System  200  as illustrated provides an practical system which may be used with several different types of standard and existing safety equipment without having to be permanently mounted to safety equipment.  
         [0056]    [0056]FIG. 10A is a front perspective view of the system of FIG. 7 coupled to a self contained breathing apparatus face piece according to one embodiment of the present invention. System  200  includes sensor unit  202  coupled to view mask  221  of self continual breathing apparatus  230  using face mask nut  222  and aperture  204  of sensor assembly  202 . Sensor assembly  202  is coupled to control unit  201  (not shown) via cable  203 , which may be positioned along an upper edge face mask  221  in a manner to reduce obscuring the view of a user. Sensor assembly  202  further includes first indicator  206 , second indicator  207  and temperature sensor  205 . In an exemplary embodiment, sensor assembly  202  may be substantially centered relative to view mask  221  thereby providing a safety system having indicators within constant peripheral vision of a user. As such, a user does not have to make an effort to monitor current ambient air temperature conditions while, for example, fighting a fire, performing a rescue, etc.  
         [0057]    In one embodiment, a user may couple sensor unit  202  to view mask  221  such as a Scott AV-2000 face mask. As such, a user may remove face mask nut  222  from facemask  221  and position sensor assembly  202  substantially centered over the top-center of facemask  221 . A user may then replace facemask nut  222  thereby coupling sensor assembly  202  to facemask  221 . Cable  203  may then be routed along a top portion of facemask  221  such that cable  203  may not obscure the vision of a user.  
         [0058]    [0058]FIG. 10B and 10C illustrate top and lateral perspective views of the system of FIG. 7 coupled to a self contained breathing apparatus face piece according to one embodiment of the present invention. Sensor assembly  202  of system  200  may be coupled to facemask  221  via facemask nut  222  and mounting channel  210  positioned about upper edge  223  of facemask  221 . Sensor assembly  202  includes first indicator  206 , second indicator  207  and sensor  205 . Housing  201  (not shown) may be coupled to sensor assembly  202  via cable  203  positioned along upper edge  223  of facemask  221 .  
         [0059]    [0059]FIG. 11 is a flow chart of a method for alerting safety personnel of unsafe air temperature conditions according to another embodiment of the present invention. The method may be deployed by system  200  illustrated in FIGS.  1 - 7  or other systems operable to deploy the method illustrated in FIG. 11.  
         [0060]    The method begins generally at step  300 . At step  301  a temperature may be sensed using a temperature sensor such as a resistive temperature device (RTD), thermistor, infra-red (IR) sensor, or other sensors operable to sense temperatures. Upon sensing a temperature, the method determines if the temperature is greater than one hundred forty degrees Fahrenheit. Although not limited to this value, the method may be used in association with firefighting systems wherein one hundred forty degrees is one example of a safe temperature level for firefighter personnel.  
         [0061]    Upon determining if a temperature greater than one hundred forty degrees Fahrenheit, the method proceeds to step  303  where the method determines the level of the measured temperature. The present method, operable to determine temperature conditions, may provide several different types of indications depending on the determined conditions as they relate to, for example, safety procedures. For example, the method may be operable to determine a plurality of temperature levels or thresholds to provide various indications based upon the determined level. For example, one group of thresholds may include an ambient air temperature between one hundred forty degrees Fahrenheit and two hundred degrees Fahrenheit; an ambient air temperature above two hundred degrees Fahrenheit for a period of eight seconds; an ambient air temperature between four hundred degrees Fahrenheit and five hundred degrees Fahrenheit; an ambient air temperature above five hundred degrees Fahrenheit for eight seconds; or a plurality of other air ambient temperature conditions as needed.  
         [0062]    Upon determining a level, the method proceeds to step  304  where the method may provide an appropriate indication for the determined level. For example, the method may determine an ambient air temperature condition of two hundred degrees Fahrenheit for a period of eight or more seconds. As such, the method may continuously illuminate indicator  206  which may be operable as a green light emitting diode or a miniature incandescent light. In another embodiment, an ambient air temperature condition between four hundred degrees Fahrenheit and five hundred degrees Fahrenheit may be determined. As such, first indicator  206  operable as a green Indicator may be continuously illuminated and second indicator  207  operable as a red Indicator may be periodically illuminated (e.g. blinking) thereby providing an overall indication reflective the determined level.  
         [0063]    Upon providing an appropriate indication, the method proceeds to step  301  where the method senses a temperature. In this manner, the method provides for sensing an ambient air temperature, determining a level, and providing an appropriate indication based upon the sensed temperature to ensure that safety personnel have a current indication of the proximal ambient air temperature condition.  
         [0064]    In one embodiment, a system deploying the method of FIG. 11 may be operable as an active system which may continuously sample an ambient temperature. As such, a system may be operable in an operating mode which may sense a temperature at a periodic rate based upon a determined temperature level. For example, a system may sense a temperature every eight seconds until a temperature level of one hundred degrees Fahrenheit&#39;s sensed. As such, the system may alter the operating mode to sense a temperature every four seconds. In this manner, the battery life of a battery associated with the system may be preserved during what may be “non-critical” temperatures thereby extending the amount of time a system may be used.  
         [0065]    [0065]FIG. 12 is a flow chart of a method for activating a safety device for alerting safety personnel of unsafe air temperature conditions according to one embodiment of the present invention. The method may be deployed by system  200  illustrated in FIGS.  1 - 7  or other systems operable to deploy the method illustrated in FIG. 12. Reference numbers, components, and elements of system  2000  of FIG. 7 are used in an exemplary form and are not intended to limit the applicability of the method of FIG. 12 as described below.  
         [0066]    The method begins generally at step  400 . At step  401 , the method determines if service is available for measuring ambient air temperature conditions utilizing a system such as system  200 . For example, a voltage regulator associated with system  200  may determine the amount of power available for operating system  200 . For example, a “power-consumption-to-operating-time” ratio may be provided for determining service availability. In one embodiment, fifteen minutes of service must be available prior to providing service for a system. If an appropriate amount of time is not available, the method may deny service and proceed to step  402  where an appropriate indication may be provided to a user. For example, both indicator  206  and second indicator  207  may blink three times indicating that service is not available due to a weak battery or power source.  
         [0067]    In one embodiment, the method may perform a diagnostic check of a system prior to providing service. For example, the method may perform a system check of electronics and associated hardware prior to allowing service. One embodiment may also include a user initiating a system check or a battery test prior to using the system.  
         [0068]    Upon determining that service is available, the method may then proceed to step  404  where the method determines a temperature level. For example, system  200  having sensor assembly  202  may sense a temperature using sensor  205 . Upon sensing the temperature, a temperature level may then be determined based upon the sensed temperature. For example, an A/D converter may be used in association with sensor assembly  202 . A converted signal representing the sensed temperature may then be used to determine the temperature level.  
         [0069]    In one embodiment, several temperature levels or thresholds may be used to determine a temperature level. For example, one embodiment may include determining an ambient air temperature of one hundred forty degrees Fahrenheit; between one hundred forth degrees Fahrenheit and two hundred degrees Fahrenheit; greater than 200 degrees Fahrenheit for eight seconds; between four hundred degrees Fahrenheit and five hundred degrees Fahrenheit; and greater than five hundred degrees Fahrenheit for eight seconds. Other temperature levels or thresholds may be used in association with the method of FIG. 12 as desired.  
         [0070]    Upon determining a temperature level, the method may proceed to step  405  where the method provides an appropriate indication for the determined level. For example, system  200  having first indicator  206  operable as a green Indicator and second indicator  207  operable as a red Indicator may be used to provide an appropriate indication of the determined temperature level of Step  404 . As such, the method may use several combinations for illuminating first indicator  206  and second indicator  207 . For example, the method may not illuminate either Indicator for a temperature of less than one hundred and forty degrees Fahrenheit; periodically illuminate (e.g. blinking) first indicator  206  for a temperature level between one hundred forty degrees Fahrenheit and two hundred degrees Fahrenheit; continuously illuminate first indicator  206  for a temperature level of greater than two hundred degrees Fahrenheit for eight seconds; continuously illuminate first indicator  206  and periodically illuminate (e.g. blinking) second indicator  207  for a temperature level between four hundred degrees Fahrenheit and five hundred degrees Fahrenheit; or continuously illuminate first indicator  206  and second indicator  207  for a temperature of greater than five hundred degrees Fahrenheit for eight seconds.  
         [0071]    Upon providing an appropriate indication, the method proceeds to step  404  where the method determines another temperature level. In this manner, several different temperature levels and associated indications may be determined and provided by the method of FIG. 12 as needed or required while providing indications of ambient air current temperature conditions to safety personnel.  
         [0072]    [0072]FIG. 13 is a block diagram of a system for alerting safety personnel of unsafe air temperature conditions according to another embodiment of the present invention. As can be seen, system  500  is similar to system of FIG. 1 and system  80  of FIG. 5. In the embodiment of FIG. 13, system  500  includes a microprocessor  501  operable to receive power from a battery and low voltage detection circuit  504 . In one embodiment, system  500  may provide a battery life of greater than four months at room temperature thereby reducing the need for replacing a battery on a frequent basis. Microprocessor  501  serves as a control unit for system  500 , which may include alternate types of control devices as mentioned above. Service of system  500  be automatically determined by processor  501  or may also be determined by operating self test push-button  50   e . Sensor unit  502  includes a first indicator  511 , a second indicator  512  and a temperature sensor  510 . Sensor unit  502  may be operable to measure temperature and may provide an output to a comparator circuit or A/D converter operably associated with microprocessor  501 . Microprocessor  501  may also be operable to provide signals to first indicator  511  and second indicator  512 .  
         [0073]    System  500  may further include a vibration alarm  507  (e.g., mechanical motor, solenoid) and an audible alarm  508  operable to provide an indication based upon a determined temperature level. Further, microprocessor  501  may include a serial port  506  which operable to output data to an infrared data port  505  for external interface to system  500 . As such, a recorded temperature history or other pertinent information may be obtained by an external device operable to communicate with system  500  via infrared data port  505 .  
         [0074]    During use, service or availability of system  500  may be determined by microprocessor  501  through accessing battery and low voltage detect circuit  504 . Upon determining if sufficient voltage or battery life is available, system  500  may determine a temperature level using sensor unit  502  and sensor  510 . Microprocessor  501  may determine an operating mode for system  500  by sampling an ambient air temperature using sensor unit  502  and providing an operating mode based upon a determined temperature. For example, system  500  may sample or sense a temperature every eight seconds for temperatures less than one hundred forty degrees Fahrenheit, and every four seconds for temperatures greater than one hundred forty degrees. As such, energy may be conserved at lower temperatures thereby extending the usable life of system  500 &#39;s battery.  
         [0075]    System  501 , upon sensing a temperature with sensor unit  502 , may then determine an ambient air temperature condition and provide an appropriate output. For example, if a temperature between one hundred forty degrees Fahrenheit and two hundred degrees Fahrenheit is determined, system  500  may provide one of a plurality of outputs available to system  500  such as using vibration alarm  507 , audible alarm  508 , indicators  511 ,  512 . As such, system  500  provides an efficient system for providing personnel an indication of current ambient air temperature conditions.  
         [0076]    Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.