Further Links Contact Us Search Help

Syllabus | Exams | Exam techniques | Resources | Teachers | Feedback

Senior Science

Home > Senior Science > Options > Disasters > Disasters: 4. Warning devices

9.8 Option - Disasters: 4. Warning devices

Syllabus reference (October 2002 version)
4. Warning devices can also be used to detect disasters associated with human activity	Students learn to: describe the energy transformation involved in the operation of a range of commonplace warning and protection devices, including smoke detectors fire alarms sprinkler systems	Students:  gather and process information from first-hand investigations to determine the type specific use location maintenance schedule of fire extinguishers located within a workplace plan, choose equipment or resources for, and perform a first-hand investigation to construct a working alarm or safety device gather information from secondary sources to identify evacuation drill procedures and assess their appropriateness in an emergency situation analyse information and use available evidence to identify appropriate locations for smoke and fire detectors in a workplace

Extract from Senior Science Stage 6 Syllabus (Amended October 2002). © Board of Studies, NSW.

[Edit: 22 Aug 08]

Prior learning: Science Stage 4-5: 4.10 d).

Background information: Fire alarms have been used for a long time but better methods have been developed to give warnings a lot earlier.

gather and process information from first-hand investigations to determine

• the type
• specific use
• location
• maintenance schedule of
  fire extinguishers located within the school and work environments

• Decide on which workplace to investigate. It could be the school or you may choose to investigate one of your parents' or older brother's or sister's workplace. If you have a part-time job you may investigate that workplace.
• If you choose the school gather information by taking a plan of your school and marking on the plan the locations of the following pieces of equipment :
  • fire blankets
  • fire extinguishers
  • fire hoses
  • evacuation maps
• Use appropriate symbols to show the locations where fire extinguishers can be found on the school grounds. Make sure that you show the different types of extinguishers used. Explain the type of fire extinguisher by matching it with the subject or activity taught in each area. For each extinguisher, find out when it was last serviced and when it is due for its next service. Use information supplied by the manufacturer to determine how the extinguisher is serviced. How should you use a fire extinguisher? Is there a diagram to show this on the extinguisher? Is it clear how it should be used?
• Use the information gathered above to draw up a plan to install smoke and fire detectors in the school if they are not already installed.

describe the energy transformation involved in the operation of a range of commonplace warning and protection devices, including

• smoke detectors
• fire alarms
• sprinkler systems

• Whenever possible, it is better to prevent a disaster than to repair the damage after the event.
• There are many types of alarms commercially available for different purposes.
• Alarms can be used to warn
  • the occupants of a building of danger from fire or electrical or other fault
  • security companies of an illegal entry in a building under surveillance.
    
• Fire alarms can
  • be used to switch on fire fighting equipment or simply warn people
  • be triggered by presence of smoke or heat
• All alarm systems must be able to respond to a stimulus. This stimulus may take on different forms such as
  • heat
  • sound
  • movement
  • light
  • presence of particles
    
• Simple fire alarms simply respond by the heat of the fire causing a bimetal strip to bend so that the metal closes a circuit that has a bell in it. When the circuit is closed the bell rings. The energy changes here are heat--> mechanical --> electrical --> sound.
• A sprinkler system responds by the heat of the fire melting a seal in a sprinkler system and releasing water through a system of sprinklers in the building on fire.
• In order to obtain a more rapid response, systems that respond to different stimuli were developed.
• Smoke detectors were developed because (in many fires), the smoke was noticeable and a risk to life before the heat of the fire was great enough to set off sprinkler systems.
• Smoke detectors use small radioactive sources which emit radiation across a small space. The radiation is detected and monitored. If there is smoke in the room, this enters the space in the detector, stopping the radiation getting through. This change is detected and sets off the alarm. In this way, a smoke alarm will warn the occupants of the building well before a conventional fire alarm.

analyse information and use available evidence to identify appropriate locations for smoke and fire detectors at home, school and the workplace

• If you choose the school as the workplace again you can use the plan of your school used before to show the locations of smoke detectors throughout the school.
• You could ask a parent or older brother or sister who works, if they could bring home a map of smoke detectors in their workplace.
• When you have the required information analyse it by studying the locations. Consider if they are in the best places or if they could be placed elsewhere to greater advantage. (Consider things like where are fires most likely to break out, would people hear the alarm if it went off and is it likely to be triggered accidentally in that location.)
• If you ring a major sporting or entertainment venue and ask them for their evacuation plans, they may not want to tell you. Why might they want to keep this information confidential?

gather information from secondary sources to identify evacuation drill procedures and assess their appropriateness in an emergency situation

• Gather information by obtaining the emergency evacuation procedures from the office or from the teacher in charge of evacuations.
• As a group, work out the quickest way of getting all students and staff out of the school buildings. Then compare your method with the school's evacuation procedures.
• Assess the school's procedure by considering if your method or the school's is the best. Why do you think the one you chose is better? Have any conditions changed since the procedure was written?

plan, choose equipment or resources for, and perform a first-hand investigation to construct a working alarm or safety device

• Consider what type of alarm or safety device could be built with the existing equipment in the school. If the equipment is very limited the teachers may consider buying an electrical kit from a hobby shop. Investigate what kits are available and if they are suitable for the investigation.
• When you have decided what type of device to build, choose the equipment.
• Perform the investigation by building the device. Test it to see if the alarm goes off when it is meant to.
• One example of a fire alarm is to have a bimetallic strip in a circuit. Bimetallic strips are made of two different metals bonded together. Observe what happens to a bimetallic strip when you heat it in the flame of a Bunsen burner. Design a fire alarm which uses a bimetallic strip to set off a warning bell in case of fire. Construct your alarm and report on whether it fulfilled its task. What problems can you foresee for a warning system that uses this method to warn people of fire.