Filter packs: Filter pack samplers were used to collect simultaneous samples of gas and bulk PM. The filter packs comprised one particle filter followed by 2-4 base-treated gas filters in an all-Teflon cartridge. Gas filters (Whatman Quantitative Filter Papers, Ashless, Grade 41, 55mm diameter) were pre-soaked with a 0.1M K2CO3 (+ glycerol) and dried approximately one week before use in the field. This base treatment of the gas filters capture acidic gases (e.g., SO2, HF and HCl). For some samples, the last gas filter in the filter pack contained >10% of the total captured gas concentration – this is evidence that the gas filters had become saturated; these gas samples are identified in the data file as 'saturated'. The particle filter collects bulk (non size-resolved) PM. The particle filter used was Whatman PTFE 47 mm diameter, pore size 0.8 µm. The filters were pre-washed with UPA grade nitric acid before use on the 2019 campaign. The filters were not pre-washed before the 2018 campaign. Field and lab filter blanks were used to quantify the level of contamination due to the absence of acid wash. The contamination was found to be negligible in most samples due to the high sampled concentrations in the eruption-affected atmosphere in 2018. Airflow through the filter pack was generated using an external 12 V pump (Charles Austin Capex) running at ~20 l min-1. The flow rate was measured at the start and end of each sampling period. The uncertainty introduced by variations in the flow rate, and by the accuracy of the flow meter are 10%.