What Makes Smoke Alarms Beep?

History

• Although the battery operated smoke detector as we know it now was invented in 1969 the smoke detector was invented by Walter Jaeger in the 1930s in Switzerland. It wasn't until 1969 when Randolph Smith and Kenneth House invented and patented the battery operated smoke detector.

Types

• There are two types of smoke detectors available to the consumer. The first is the ionization detector, which uses a radioactive source to detect smoke. The second is the photoelectric cell detector, which uses an optical sensor to measure the intensity of light and goes off when it "sees" smoke.

How Do They Work?

• Ionization smoke detectors are the most common and use a radioactive source to create an electrical circuit. Breaking the circuit causes the alarm to go off. The circuit can be broken if there is enough smoke in the air to prevent the flow of electrons.

Safety

• Smoke detectors that are battery operated should be tested at least once a month to ensure that the battery has enough charge to operate the detector. Smoke detectors have expiration dates and should be replaced after 10 years. This is because of the radioactive isotope inside the detector.

Sizes and Shapes

• Smoke detectors today come in many different sizes and shapes. Some detectors have been miniaturized and some have even been designed to match decor and decorating styles.