In the United States (U.S.), physical inactivity is the fourth leading cause of death, with an estimated 200,000 deaths annually (Danaei et al., 2009). The lack of activity across the life span is important because it is a welldocumented risk factor for leading non-communicable diseases including cardiovascular disease, cancers, obesity, and type 2 diabetes, as well as impaired quality of life (U.S. Burden of Disease Collaborators, 2013; U.S. Department of Health and Human Services, 2008). The need for policies and environments that promote population-wide increases in physical activity is important, given that only half of U.S. adults meet the recommended 150 minutes of moderate intensity physical activity weekly, 75 minutes of vigorous intensity activity, or an equivalent combination (U.S. Department of

BackgroundIn 2014, residential fires caused 2745 civilian deaths in the United States (US) and almost 12,000 injuries. Smoke alarms are an effective intervention for reducing residential fire deaths. Innovative strategies are needed to improve the prevalence of working smoke alarms in homes. We used Facebook advertising to encourage participation in a free smoke alarm installation program in one US city.MethodsAs part of a larger evaluation of an enhancement to a smoke alarm distribution program, we developed three ads that ran on Facebook throughout October 2014 with a US$100 daily budget. The ads included three different images and a motivational message. The ads appeared on the news feeds and mobile news feeds of adult Baltimore City residents.ResultsThe three ads delivered to desktop and mobile device news feeds resulted in 465,666 impressions and reached 130,264 discrete users (43% of those 300,000 users estimated to be eligible). Most users viewed the ads on a mobile device (99%). Of the Facebook users reached, 4,367 different users (3.4% unique click-through rate) clicked the ad. Some users clicked through more than once, resulting in 6,075 total clicks. Mobile devices yielded higher click-through rates than desktops (1.31% and 0.36% respectively). Of the 4,367 unique clicks, nearly all (4,357) came from mobile devices.The cost per impression was less than one cent. We spent two cents to reach each user, and 70 cents on each unique user who clicked on the ad. For those 25 participants who requested a smoke alarm installation and cited Facebook as their information source about the program, we spent $124 to achieve that target behaviour.ConclusionsFacebook advertisements are a novel approach to promoting smoke alarms and appear to be effective in exposing individuals to a service program. However, converting Facebook message recipients into users of a smoke alarm installation program occurred infrequently.

Facebook advertisements are a novel approach to promoting smoke alarms and appear to be effective in exposing individuals to injury prevention messages. However, converting Facebook message recipients to users of a smoke alarm installation program occurred infrequently in this study. Residents who participated in the smoke alarm installation program were more likely to cite the automated call as the impetus for their participation. Additional research is needed to understand the circumstances and strategies to effectively use the social networking site as a tool to convert passive users into active participants.