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

ate of fire growth (table 32). Average time for flaming fires was significantly longer in the 1975tests than in the current study – 969 s versus 131 s. Average times for smoldering fires in thecurrent test series were comparable to those observed in the 1975 tests. It is important to note,however, that the smoldering fire scenarios are very difficult to reproduce experimentally, andthat times in the present study has an uncertainty (based upon one standard deviation) whichoverlaps the uncertainty in the 1975 study. Therefore, caution should be exhibited in drawingconclusions based upon comparisons of smoldering tenability times between the two studies.While the 1975 study also used actual upholstered furniture and mattresses, these werepurchased from a (charity) resale shop from donated articles. Such items purchased in 1975would have been new in the early 1960s or even late 1950s and represented materials andconstructions of that period. The chairs used in the present study were purchased from afurniture rental store and, while used, were only a year or two old. The mattresses werepurchased new. Thus, the materials were certainly significantly different. Fire development inthe current tests showed generally similar timing in growth of heat release rate to other recentstudies for upholstered furniture [53] and mattresses [54].In the upholstered furniture study, a set of upholstered chairs was constructed from five differentfabric/foam combinations and subjected to a variety of ignition sources suggested by firestatistics. In the study, an effort was made to choose from across the spectrum of typicalresidential materials although no statistical justification for the particular materials was made.Time to peak heat release rates in excess of those necessary to lead to untenable conditions instructures in the current study ranged from about 150 s to nearly 1000 s. It is estimated that acomparable value for chairs in the current study is about 300 s. For mattresses, time toincapacitation using similar criteria to the current study ranged from 240 s to 1150 s, dependingupon the mattress. It is important to note that this study included reduced flammability designsnot currently on the market. Thus, the materials used in the current study should not bedramatically different than other currently available materials. Still, it is important to note thatwhile both the 1975 study and the current study attempted to use a representative sample ofavailable and important furnishings, each study included only a small fraction of those availablein the marketplace.Conversely, alarms in the current study were, on average, of similar sensitivity compared to thealarms in the 1975 study. In the current study, the sensitivity of the unmodified smoke alarmswere discussed in section 2.6. The average sensitivity measured for all alarms tested was1.54 %/ft ± 0.45 %/ft. In the 1975 study, the average of all alarms tested was 1.91 %/ft ±0.73 %/ft. While the average for the 1975 tests is higher, the uncertainty in the data overlaps.249