Performance of Home Smoke Alarms - National Institute of ...

Table 9. Locations for primary optical density measurements in tests of smoke alarm responseStructureManufacturedHomeTwo-StoryHouseLocationBedroom 2 (remote bedroom) 20, 900Bedroom 1 (room of fire origin for mattress tests) 20, 900Hallway 1 (outside bedroom 2) 20, 900Hallway 2 (outside bedrooms 1 and 3) 20, 900Living area (room of fire origin for upholstered chairand cooking oil tests)Vertical Positions(mm from ceiling)20, 900Hallway 2 (near living room) 20, 900Bedroom 3 (closed bedroom) 1020Bedroom 2 (remote bedroom) 20, 900Second floor hallway 20, 900First floor foyer 20, 900First floor den 20, 900The main function of the field test smoke meters was to provide obscuration data for assessingtenability limits. An optical density of 0.25 m -1 (1.5 m from the floor) was used in the analysisas the tenability criterion for smoke obscuration. It is important to note that heat transfer fromhot gases transported to the smoke meters causes their voltage output to drift, giving a falseindication of smoke and a larger apparent optical density than what would be due to the smoke inthe optical path. The time after a significant amount of heat transfer occurred represents a periodof smoke meter operation where the smoke obscuration results would not be reliable.Smoldering fire tests typically did not produce significantly elevated temperatures, thus theuncertainty in a smoke meter obscuration measurement during smoldering phases is essentiallythe ambient temperature calibration uncertainty. Laboratory tests on un-insulated and insulatedsmoke meters indicated that a temperature change approximately 20 EC to 40 EC over 100 s to200 s, would start to affect the reliability of the computed smoke obscuration by the end of theheating period (the insulated meters performed better.) Therefore, caution must be used whenanalyzing these smoke meter results anytime the ambient temperature has changed. During theflaming phase of these tests, the optical density tenability limits were reached prior to significantsmoke meter heating.86