This work assessed the potential impact on mortality and life expectancy that would occur due to reductions of indoor PM2.5 in dwellings in the UK using portable air purifiers. Reductions in indoor PM2.5 concentrations from air purifier use were modelled using findings from the literature for mean air purifier efficiency, mean indoor PM2.5 concentrations associated with air purifier use, and the relative risks associated with exposure. Life-table models were used to estimate changes to mortality from the following PM2.5-associated diseases: lung cancer, lower respiratory infection (LRI), chronic obstructive pulmonary disease (COPD), ischemic heart disease (IHD), and stroke. Different scenarios were modelled to represent a range of daily use patterns, the starting age of use and the duration of the intervention. The overall impact of the central scenario, in which air purifiers were used during all hours whilst at home (15.6 h) for the entirety of the modelled period (birth to 97 years), was to increase life expectancy in the birth cohort by, on average, 138 and 120 days for males and females, respectively, and to add more than 23 million years of life (YLG) to the UK population. When used at home, air purifiers reduced indoor PM2.5 concentrations and prolonged life expectancy, but questions regarding feasibility of the intervention, occupant behaviour and social inequities remain. The estimation of the impact of use by the whole population is, however, important for informing policy and designing interventions.