Second-hand smoke (SHS) exposure is a serious health hazard for children, contributing to harms including glue ear and meningitis. A range of interventions to protect children from SHS have been developed with varying success. One area that shows promise is personalised feedback interventions, using measures such as household air quality to encourage parents to keep their homes smoke-free. Measuring for Change is a pre-post study with arms in four European countries, testing a novel air quality feedback intervention. The study, which runs from 2016-2018, uses a new low-cost air quality monitor and innovative text- and email-based communications with parents/carers, to develop an inexpensive intervention which offers rapid feedback on the impact of smoking on indoor air quality to motivate behaviour change and encourage parents to make their homes smoke-free. This presentation will discuss a) the roots of the Measuring for Change study in a previous intervention development project (AFRESH), b) the process and the aims of the study, and c) our learning experiences from the early stages of the work. Measuring for Change is part of the TackSHS project, funded by the European Union’s Horizon 2020 Programme (Grant No 681040).