How is the percent per foot obscuration of a smoke detector determined during sensitivity testing?

How is the percent per foot obscuration of a smoke detector determined during sensitivity testing?

• A. By manufacturer recommendations.
• B. Based on observed nuisance alarms.
• C. Detectors are marked with sensitivity tolerance.
• D. By field test with aerosol.

Answer: (C)

Percent obscuration per foot is a device-specific sensitivity specification. Each smoke detector is designed to respond to a certain density of smoke along its sensing path, and the manufacturer labels a tolerance range for that sensitivity on the unit or in its data sheet. During sensitivity testing, you compare the measured obscuration required to trip the detector to this labeled tolerance. If the observed value falls within the marked tolerance, the detector passes that aspect of the test and is considered within spec. This approach provides a consistent, manufacturer-defined standard across units. Other options don’t set the standard value. A field aerosol test can show how a unit performs in a particular setup, but it doesn’t define the device’s official sensitivity tolerance. Nuisance alarms are an indicator of issues but don’t establish the rated obscuration. Manufacturer recommendations guide procedures, but the actual, enforceable tolerance is the value the device itself is marked with on its label or data sheet.

Percent obscuration per foot is a device-specific sensitivity specification. Each smoke detector is designed to respond to a certain density of smoke along its sensing path, and the manufacturer labels a tolerance range for that sensitivity on the unit or in its data sheet. During sensitivity testing, you compare the measured obscuration required to trip the detector to this labeled tolerance. If the observed value falls within the marked tolerance, the detector passes that aspect of the test and is considered within spec. This approach provides a consistent, manufacturer-defined standard across units.

Other options don’t set the standard value. A field aerosol test can show how a unit performs in a particular setup, but it doesn’t define the device’s official sensitivity tolerance. Nuisance alarms are an indicator of issues but don’t establish the rated obscuration. Manufacturer recommendations guide procedures, but the actual, enforceable tolerance is the value the device itself is marked with on its label or data sheet.