How do Smoke Detectors Work?

Image of Smoke around a Smoke Detector

How Do Smoke Alarms Work?

You count on your smoke detectors to keep you safe, but have you ever wondered how they work?

First, it’s important to know there are two types of smoke detectors: ionization smoke detectors and photoelectric sensors.

You can safely use either one, but safety experts recommend using both for total protection of your home and family.

Did You Know?

  • A smoke detector is also known as a fire alarm, but its official name is a smoke alarm.
  • According to the Underwriters Laboratory, modern homes burn eight times more quickly than homes built between 1950 and 1970.
  • The National Fire Protection Association says most fire deaths occur in homes where there was no alarm or the alarm wasn’t working.

All smoke detectors have the same basic setup. They have a sensor to detect smoke and a device that transmits a warning noise. They can run on batteries or on the house current.

Ionization Smoke Detectors

An ionization detector works like other alarms in your house. It relies on two sensors that maintain a connection. When smoke disrupts that connection, the break triggers an alarm.

The alarm’s battery contains wires that attach to separate electrodes. These electrodes complete a wiring circuit without touching each other. Instead, they use a small amount of americium-241, which is a radioactive material.

The americium-241 creates alpha particles that ionize the molecules between the electrodes. These ions maintain a connection that doesn’t require physical attachment.

When smoke enters the detector’s housing, it disrupts the connection between the electrodes. This causes the alarm’s inner circuit to trip and sound the alarm.

Benefits of Ionization Alarms:

  • They are excellent at detecting flames. Most house fires have fast-moving flames and very little smoke. An ionization alarm can detect fire when it first starts.
  • They are inexpensive and easy to install.
  • These alarms are widely available. More than 90% of American homes have ionization smoke detectors.

Photoelectric Smoke Detectors

Also known as optical smoke alarms, these detectors use LED lights to detect smoke.

A photoelectric alarm uses a photo beam detector to connect an LED light to a sensor on another part of the wall or ceiling. The beam that connects them is invisible to us. As long as the sensor can connect to the light, it maintains an electrical circuit.

When smoke enters the alarm’s housing, it covers the LED light. The LED then sends light to a second sensor. The light triggers this second sensor to sound an alarm.

Benefits of photoelectric smoke alarms:

  • They can detect smoke from smoldering fires before they burst into flame.
  • They are long-lasting and durable.
  • They respond quickly.

Keep Your Smoke Detectors Working at Peak Performance

Follow these tips to stay safe.

Use Both Types of Alarm

The National Fire Protection Association says, “You should use both ionization and photoelectric technologies in homes. Combination alarms that include both technologies in a single device are available.”

You never know what type of fire you’re going to have. With both types of detectors in your home, you can protect yourself from fast flames and smoldering fires.

Test Them Regularly

You should test your alarms once a month. Use this time to wipe dust and dirt out of the alarm’s housing. Replace the batteries as soon as you get the “low battery” warning.

Replace Them

You should replace all smoke detectors when they’re 10 years old. If your detector is old or isn’t working properly, ask your electrician to install a new one.

Safety First With SESCOS

If you need help testing your smoke alarms or installing new ones, contact SESCOS today. We’re here to help you stay safe.

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