Evaluating the Cost-Effectiveness of Interlinked Fire Alarm Systems in Scotland and England

Abstract This paper applies the J value framework to assess when interlinked domestic fire alarm systems would be cost effective in Scotland and England. Pre policy national statistics pool dwellings with no alarms, standalone alarms (the vast majority), and some interlinked systems, so they do not identify the marginal effect of interlinking. We therefore present threshold (break-even) conditions: combinations of reductions in fatalities, injuries, and direct property damage that yield J ≤ 1 for self and professional installation, using historical statistics only as non-causal, illustrative anchors for sensitivity analyses. It was found that, across both countries, damage reduction is the dominant driver of cost-effectiveness, followed by fatality reduction; injury reduction has limited influence (assuming direct injury costs only). One-way thresholds indicate that achieving $$\:J\le\:1$$ typically requires around 30–60% reduction in direct property damage, with fatality thresholds generally around 40–80% depending on installation method and region. Two-factor (damage and fatality) thresholds show trade-offs between these reductions, with more demanding conditions in England due to higher expected damage per fire. Tornado analyses centred on an illustrative base case confirm that installation cost and damage-related inputs exert the greatest influence on $$\:J$$ , while societal discount rates have modest effects. Interlinked systems can be cost effective where installed costs are lower (for example self-installation) and reductions in property damage, and secondarily fatalities, are moderate to large. Improved data on alarm type and performance, property-damage costs, and near-misses would enable movement from threshold analysis to causal evaluation.