Multiple Sensor Detectors

Q: In regards to multi-sensor devices, such as rate of rise/fixed temp combo heat detectors; if the rate of rise portion of the device is testable, but the fixed temp portion of the device is not, then does the device fall into the replace after 15 years for non-restorable heat detectors? The same issue with smoke/fixed temp heat combo devices (older devices); do they have to be replaced for the fixed temp heat portion? There are many different ways to view this, as code states that they have to be tested independent of one another.

A: The short answer is no, combination devices do not fall into the 15 year replacement criteria.  Explanation: The replacement interval for fixed temperature heat detectors applies only to non-restorable detectors [NFPA 72 Table].  Both smoke/heat and rate of rise/fixed detectors are restorable.  Rate of rise/fixed heat detectors fall under the maintenance requirements of Table, which does not mandate a replacement interval.  If the rate of rise tests normally, that’s the primary sensor and does not have to be replaced as long as it passes inspection. Smoke/heat detectors fall under two maintenance criteria.  Table is for smoke detectors with thermal elements, which states that both elements must be tested & the failure of any element requires the replacement of the device.  However, since we’re talking about a smoke/heat detector with a fixed temperature element, Table for combination fire detectors is applicable.  It states that if individual sensors cannot be tested individually, the primary sensor shall be tested, in this case being the smoke detector.  As long as the primary sensor functions properly, it’s good to go and is the sole consideration regarding replacement.