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The Smoke Detector Difference

Inspecting the location of smoke detectors is something that all home inspectors do. I still can’t believe the homes that do not have working or properly places smoke detectors. You would think that with all the publicity, everyone would understand the importance of them. This year at the Niagara Frontier Home Inspectors Training Conference, we will have an expert in Fire and Safety (Mel Shaw) discussing this issue. Using just a “basic” old style smoke detector is no longer acceptable. What exactly is the difference, and how can a home inspector properly advise the client? Ionization smoke alarms are responsive to flaming fires. Ionization smoke detectors have a small amount of radioactive material between two electrically charges plates, which ionize the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of current and activates the alarm. Photoelectric smoke alarms are more responsive to smoke or smoldering fires. They aim a light source into a sensing chamber at an angle away from the sensor. Smoke enters the chamber reflecting light onto the light sensor, triggering the alarm. How can a home inspector tell the difference and properly advise their client?

A home inspector should advise their client to have a combination type (Photoelectric & Ionization) smoke detector. Here is how to tell the difference between Photoelectric, Ionization and Combination type smoke alarms:

Ionization Smoke Alarms

  • A look case letter “i”
  • The word “ionization”
  • The phrase “contains radioactive material”
  • The symbol for radioactive material

Photoelectric Smoke Alarms

  • A capitol letter “P”
  • The word “Photoelectric”
  • The phrase “Photoelectric Technology”

Combination Ionization & Photoelectric Alarms

  • May have the words; “photo” & “ion”
  • A capitol letter “P” and lower case “i”
  • The words “Photoelectric” and “Ionization”
  • The words “Photoelectric Technology”
  • The phrase “contains radioactive material”

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