My Smoke Alarm Report

By someone


Smoke alarms are a great invention that saves tons and tons of lives. They can work in strange ways. Did you know that smoke alarms started out as heat detectors, made from butter? This report explains many more of the interesting facts about smoke alarms. In this report I’ll teach you about the history of smoke alarms and how they work. I’ll also teach you about what it actually is and does.                      


Who invented the smoke alarm? According to Ian Sinclair, Danielle Lindgren, Minzee Kim, Babak Oskoui, and David Windseth, (, “Smoke detectors have come a long way since George Darby first invented in 1902.” Which means that in 1902 a man named George Darby invented the smoke alarm.

What did people use before smoke alarms were invented? Before smoke alarms, scientist used and open/ close electrical system. Ian Sinclair, Danielle Lindgren, Minzee Kim, Babak Oskoui, and David Windseth, said” his system’s setup included two plates or electrical circuits, with a wedge of butter between them. When the heat of the room became overwhelming and dangerous, the butter would melt, causing the two circuits to collapse onto one another, initiating the alarm.”

What might happen with smoke alarms in the future? Ian Sinclair, Danielle Lindgren, Minzee Kim, Babak Oskoui, and David Windseth, (, say” New sensors, analog sensors, are being installed in today’s new detectors. These sensors send information to a control computer, which can detect whether the detectors themselves are too dirty to function or if they are too sensitive for the area in which they are placed.” There are many ways that smoke alarms can be improved.

How it Works.

Have you ever wondered how a smoke alarm works? Since there are two different kinds of smoke alarms, they work in two different ways. There is and ionization alarm, and a photoelectric alarm.

Photoelectric alarms. The photoelectric alarm works with a ray of light and a sensor. It is in a T shaped chamber with an LED at one end. When smoke enters the chamber, it distorts the light and it goes down the vertical part of the chamber to the sensor, and triggers the alarm. According to Anne Marrie Helmenstine (, “In one type of photoelectric device, smoke can block a light beam. In this case, the reduction in light reaching a photocell sets off the alarm.”

Ionization alarms. Ionization alarms work with radiation. Anne Marrie Helmenstine (, says,” The ionization chamber consists of two plates. The battery applies a voltage to the plates, charging one plate positive and the other plate negative. Alpha particles constantly released by the americium knock electrons off of the atoms in the air, ionizing the oxygen and nitrogen atoms in the chamber.The positively-charged oxygen and nitrogen atoms are attracted to the negative plate and the electrons are attracted to the positive plate, generating a small, continuous electric current. When smoke enters the ionization chamber, the smoke particles attach to the ions and neutralize them, so they do not reach the plate. The drop in current between the plates triggers the alarm.”

What it is and does.

What a smoke alarm is. A smoke alarm is a device used to detect smoke and warn people in the building. It is circular and usually white. There are two different kinds, ionization, and photoelectric.

Is photoelectric or ionization better? According to Anne Marrie Helmenstine (, “Both ionization and photoelectric detectors are effective smoke sensors. Both types of smoke detectors must pass the same test to be certified as UL smoke detectors. Ionization detectors respond more quickly to flaming fires with smaller combustion particles; photoelectric detectors respond more quickly to smoldering fires. In either type of detector, steam or high humidity can lead to condensation on the circuit board and sensor, causing the alarm to sound. Ionization detectors are less expensive than photoelectric detectors.” So they are both good.


Smoke alarms are an amazing invention. Thanks to George Darby, we have inventions that alert us when there’s fire.