Background  Accurate measurement of respiratory aerosols is challenging because exhaled particle concentrations are extremely low and difficult to distinguish from indoor background aerosol. As measurements are often collected at a single time point, it remains unclear how individual emission rates vary over time and whether high emitters remain high over extended periods.  Methods  We developed a measurement approach to quantify respiratory aerosol emissions under non-ultra-clean indoor conditions. Exhaled particles were measured using an Aerodynamic Particle Sizer while participants wore a tightly sealed facemask connected to the instrument. Background aerosol was minimised by filtering inhaled air through five low-resistance filters and using air purifiers to reduce indoor particle concentrations. Participants completed a standardised sequence of breathing and speaking activities. Measurements were performed on Days 0, 1, 7, 14 and 28 (n = 43), with follow-up at Day 180 when available (n = 28).  Results  Individuals exhale consistent levels of aerosol over extended periods when breathing and speaking, although with large inter-individual variations. A subset of participants consistently emitted substantially more particles than others, up to 180 days in those with follow-up. Within the sampled age range, aerosol emissions showed a positive association with age across activities, whereas associations with height, weight and BMI were weaker.  Conclusion  Robust longitudinal respiratory aerosol measurements can be achieved outside ultra-clean environments using effective background filtration. Persistent high emitters over months highlight stable heterogeneity that should be considered in indoor exposure assessment and airborne transmission risk.