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How do smoke detectors work?

A smoke detector is an amazing device that helps us detect the smoke to prevent us from fire hazards. This is a device that is doing his job perfectly and silently to keep us safe.


Have you ever thought about it how do smoke detectors work? Or how they can easily detect the smoke and notify us?

I guess, this question recently hits your mind and that is why you are here to read this article. Well, you are in the right place. I will explain to you how easily and exactly smoke detectors work.

Types of smoke detectors?

Before going to the main part, you need to know that there are two types of smoke detectors in the market, and both work differently. That is why you need to know the types of smoke detectors at first. The types are:

  1. Optical/photoelectronic smoke detector
  2. Ionization smoke detector

How optical smoke detector work

Optical smoke detector, also known as a photoelectronic smoke detector, works best to detect smoldering fires—especially those that begin with a long time of smoldering. That is why sometimes, it is called a smoldering detector as well.

It sounds when the LED light inside the alarm chamber is broken. It is similar to a door or window photoelectronic alarm where an invisible beam of light passes through the sensors. They are not connected physically but the alarm sounds when the beam is broken.

So here is how exactly optical or photoelectronic smoke works. It is pretty simple actually.

  • There is an LED casts light in the straight line across its inner chamber.
  • At the other end, a photoelectric sensor is available that detects the light to tell the system that the circuit is fully complete.
  • When the smoke enters the housing, the light gets interrupted by the smoke just entered. As a result, the light cannot pass thoroughly and completely.
  • This interrupted smoke makes some of the light redirect to a different sensor.
  • Whenever this different sensor detects those interrupted and redirected light, it sounds the alarm.

Sounds simple and easy, right? It is easy actually.

How ionization smoke detector work

Another type of smoke detector is the ionization smoke detector. This type of detector is good for detecting fast, raging fires and flames. If you want to know how smoke detector work, you need to know how ionization smoke detector works as well.

This type consists of radioactive material in a small amount that goes through two electrically charged plates to create an ionization chamber.  With this configuration, it ionizes the inside air and makes a current flow through the plates. Whenever the smoke goes into the space, it absorbs the alpha particles and also, disturbs the ionization process. As a result, the current gets reduces and the alarm starts ringing.

  • There are wires extend from the positive as well as negative ends of the battery in the smoke detector to separate the electrodes.
  • The electrodes are there to complete the circuit, but not physically. Instead, an Americium-241 transforms the air molecules through the electrodes into positive as well as negative ions.
  • Its charged ions between these two plates then complete the circuit.
  • When any fire happens, the smoke enters the alarm through holes or slits designed in the housing.
  • Then the positive and negative ions find the smoke, not the plates and as a result, the circuit gets broken.
  • When the circuit gets broken, the alarm sounds.

It is simple as well, right?

Which one is the best?

Now you know how both of them work. So simply a question comes to the mind that which one is the best between these two. Well, compared to photoelectric alarms, Ionization type alarms provide a better response when it comes to flaming. On the other hand, photoelectric alarms generally provide faster response to smoldering fires compared to ionization type alarms. So there is no best actually.

So should you purchase a smoke detector?

So if you ask me should you purchase a smoke detector or not, I will suggest you buy one. Why?

Well, there are many reasons actually. When you have any smoke alarm, it will help you get notified when it detects any fire or smoke. As a result, you can be aware of the smoke or fire and take necessary measures to prevent any hazard. That means by investing a small amount of money on this small device, you can get rid of fire hazards. It will save you, your family, and your building from fire hazards. That is why everyone should buy such security devices such as smoke detectors, gas detectors, or carbon monoxide detectors.


The smoke detector is a very useful device we can have. When we know how do smoke detectors work, it becomes easy to understand their way of working and their importance. Now you know why it is important to have a smoke detector at your home and how it can save you from fire hazard. So make sure you install a smoke detector and have peace of mind all the time.

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