Fire  Detection Despite careful attention to the location, design, construction, and operation of the AIS facility, there is still  the  possibility  of  a  fire.  Experience  shows repeatedly that prompt detection is a major factor in limiting  fire  damage.  Typically,  a  fire  goes  through three stages. Some event, such as a failure of electrical insulation, causes ignition. An electrical fire will often smolder for a long period of time. When an open flame develops, the fire spreads through direct flame contact, progressing  relatively  slowly,  with  a  rise  in  the temperature  of  the  surrounding  air.  The  duration  of  this stage is dependent on the combustibility of the materials at   and   near   the   point   of   ignition.   Finally,   the temperature  reaches  the  point  at  which  adjacent combustible  materials  give  off  flammable  gases.  At this point, the fire spreads rapidly and ignition of nearby materials will result from heat radiation as well as direct flame contact. Because of the high temperatures and volumes of smoke and toxic gases associated with this third stage, fire fighting becomes increasingly difficult and often prevents people from remaining at the fire site. Given the objective to discover and deal with a fire before  it  reaches  the  third  stage,  one  can  see  the limitation of fire detection that depends on detecting a rise in air temperature. For this reason, the areas in which electronic equipment is installed should be equipped   with   products-of-combustion   (smoke) detectors.  Such  detectors  use  electronic  circuitry  to detect the presence of abnormal constituents in the air that are usually associated with combustion. In designing an effective fire detection system, consider the following points: Location  and  spacing  of  detectors.   The location  and  spacing  of  detectors  should  take into consideration the direction and velocity of air flow, the presence of areas with stagnant air, and the location of equipment and other potential fire sites. Note that detectors may be required under the raised floor, above the hung ceiling, and in air-conditioning ducts as well as at the ceiling. It may also be wise to put detectors in electric  and  telephone  equipment  closets  and cable  tunnels. Control  panel  design.   The  design  of  the detection control panel should make it easy to identify the detector that has alarmed. This implies that the detectors in definable areas (for example, the tape vault, the east end of the 4-20 computer room, and administrative offices) should be displayed as a group on the control panel. In other words, when an alarm sounds, inspection of the control panel should indicate which area or zone caused the alarm. Generally, and preferably, each detector includes a pilot light that lights when the detector is in the alarm state. In some cases there should be a separate indicator light at the control panel for each detector. It is also important to see that the alarm system itself is secure. Its design should cause a trouble alarm to sound if any portion of it fails, or if there is a power failure. Take steps to assure the system cannot be deactivated readily, either maliciously  or  accidentally. Personnel   response.   Meaningful   human response to the detection and alarm systems is necessary if they are to be of any value. This means  the  fire  detection  system  should  be designed to assure that someone will always be alerted  to  the  fire.  Typically,  the  computer  room staff is expected to respond to an alarm from the AIS  facility  alarm  system.  A  remote  alarm should also be located at another point in the building that is occupied at all times, such as the lobby  guard  post,  security  center,  or  building engineer’s  station.  This  provides  a  backup response   when   the   computer   area   is   not occupied. If there is any possibility the remote alarm point will not be occupied at all times, a third alarm point should be located offsite, usually   at   the   nearest   fire   station   or   the command’s fire department for the facility. Maintenance.  Proper  maintenance  is  essential to the fire detection system. The nature of smoke detectors is such that nuisance alarms may be caused  by  dust  in  the  air  or  other  factors. Because of this, there is a tendency to reduce sensitivity  of  the  detectors  to  eliminate  nuisance alarms, with the result that detection of an actual fire may be delayed. To ensure proper operation, see   that   qualified   personnel   (a   vendor representative, building engineer, or Public Works   Center   personnel)   verify   correct operation at the time of installation, and at least once  each  year  thereafter.  Furthermore,  each fault  condition  should  be  corrected  immediately. Unfortunately,  a  common  tendency  is  to  turn  off the fire detection system or silence the alarm bell, creating the danger that there will be no response if a fire should occur.