Summary ?C UL's Rationale and Proposal to Improve Smoke Alarm Performance A smoke alarm is an important defense for protecting people in homes in case of a fire threat. UL has been a leader in facilitating the development of standards for performance of smoke alarms for more than four decades starting with collaboration with NIST to develop the first standard on smoke detectors (UL 217) and subsequent collaborative field experiments known as the Indiana Dunes Study. Smoke alarms are now ubiquitous in U.S. homes with 96% homes having smoke alarms according to a recent NFPA survey. Over the last four decades@ there has been a shift in the materials used in home furnishings from natural (e.g.@ wood@ cotton) to synthetic (e.g.@ plastics) materials. A UL investigation was conducted to understand how this shift to synthetics influences smoke alarm responsiveness using a range of contemporary materials used in homes. The investigation found that some of the synthetic materials used in furnishings have smoke characteristics (e.g.@ particle size@ distribution) different from the current materials used for evaluating smoke alarms. The UL research led to identification of two new tests (i.e.@ smoldering and flaming polyurethane foam) that would increase the range of smoke particle types for testing the performance of smoke alarms@ and thus make them more responsive to current fire threats in homes. Additionally@ smoke alarms in some instances are activated during normal events@ such as cooking. These unwanted or nuisance alarms sometimes result in home occupants disabling the smoke alarms and thus eliminating an important safety feature. Statistics reveal that fatalities are twice as high in homes that do not have any working smoke alarms as compared to home fires with working smoke alarms. Thus@ another research project was conducted by UL to develop data on smoke characteristics and levels from normal cooking events that sometimes lead to nuisance activation. In this research@ several cooking scenarios were investigated to develop data on smoke particle size and distribution. Based upon this data as well as literature review@ three cooking events were identified: (i) toasting bread; (ii) pan frying hamburgers; and (iii) broiling hamburgers. Toasting bread had relative small particles@ but high particle concentration; pan frying a hamburger had a broader particle distribution; and broiling a hamburger had the largest particle size of the three events. These three cooking events were used in representative kitchen and room configurations to develop data on the smoke levels generated during normal cooking. Results from the experiments showed that broiling a hamburger generated the highest smoke levels and activated the smoke alarms most frequently. Broiling a hamburger also had particle size distribution that encompassed the other two cooking events. These results indicate that broiling a hamburger may be used as a representative scenario for testing smoke alarms for their resistance to nuisance activation from cooking events. Results from different room size configurations showed that an 8 ft. ceiling height configuration resulted in higher smoke signals than a 10 ft. ceiling height configuration. The information from these tests was used to develop parameters for standardized testing using broiling hamburger cooking scenarios. The parameters included (i) test configuration; (ii) developing a standard hamburger with 25% fat content; (iii) the number of hamburgers to broil to attain similar smoke levels in UL's standard fire test room; and (iv) the test duration. These parameters were used in UL's standard fire test room to develop smoke signal data. The results from UL research have been used to develop proposals for revision to the UL 217 standard and incorporate two new tests using smoldering and flaming polyurethane foam@ as well as a new test for evaluating smoke alarms with respect to nuisance tripping from cooking events.