SMOKE ALARM ( DESIGN ) 75 PAGES : CHAPTER 1-5
CHAPTER 1: INTRODUCTION
A smoke alarm is a device that senses smoke, typically as an indicator of fire. It may issue a signal to a fire alarm control panel as part of fire alarm system, especially in commercial security devices or may issue a local audible or visual alarm in the household .
Fire detection has become a crucial aspect in design of buildings, both commercial and domestic, as opposed to about 70 years ago when automatic detection was rarely provided in buildings. Before introduction of smoke and fire alarms, fires resulted in the loss of human lives and damage of property and it was mainly attributed to lack of a mechanism for early detection of fire. Early developments in design of smoke alarm began in 1922 with observations by Greinacher and later by Walter Jaeger in 1930. However, early smoke detectors required high voltage power input. Further research was done and power requirement in smoke detectors was reduced to make battery power viable and this made widespread installation in residences highly feasible. Later developments in smoke detectors have sought to improve their performance, reduce power requirement, improve their nuisance alarm sensitivity and also to continuously monitor their status. The most recent advances in smoke detectors have been motivated to make them „smarter‟ .
Smoke can be detected either optically (photoelectric) or by physical process (ionization). Detectors may use either or both methods.
Smoke detectors have prior detection when compared with heat detectors, hence are preferred for fire detection. They also find application in detecting, and thus deter smoking in premises where it is banned.