Texas Fire Alarm License Practice Test

How does an Ionization Smoke detector work?

1. It uses a fan to draw in smoke for detection

2. It utilizes a small amount of radioactive material to ionize the air

3. It heats air to detect smoke particles

4. It relies on changes in air pressure to detect particles

The correct answer is: It utilizes a small amount of radioactive material to ionize the air

An ionization smoke detector operates by utilizing a small amount of radioactive material, typically Americium-241, which ionizes the air within a detection chamber. This process creates a steady flow of current between two electrodes inside the chamber. When smoke enters this ionized air space, it disrupts the flow of ions and subsequently reduces the current. The detector senses this drop in current, interpreting it as the presence of smoke, which triggers an alarm. The mechanism relies upon the ionization process, making it particularly sensitive to fast-burning fires that produce little visible smoke. This sensitivity is due to the changes in the ionization levels caused by smoke particles, which are primarily responsible for activating the alarm system in a meaningful way.