Air pollution is one of biggest environmental risks to global human health. Peat fires can cause extensive pollution events, which have been correlated with adverse local community health impacts. Despite these concerns, the current understanding of particle chemical composition, as well as the concentration of ultrafine particles is limited. These knowledge gaps lead to uncertainties in emission inventories and toxicology studies. This research investigated the physicochemical characteristics of particle emitted during the smouldering combustion of six different peats. Fine particles (diameters < 2.5 μm) accounted for >85% of the total particle mass, and ultrafine particles (diameters < 0.1 μm) accounted for >81% of the total particle number concentration. Carbon and inorganic species accounted for >64% and 3 to 22% of total particle mass, respectively. Particle morphology also varied from irregular-shapes to clusters of particles held in an organic matrix. Emission factors (EFs) were calculated for the first time for Canadian, Latvian, and Scottish peat burns, as well as for Irish and Indonesian peat burns. The fine particle mass EFs ranged from 5 to 33 g kg-1, whilst number-weighted EFs ranged from 0.3 × 1015 to 4.6 × 1015 kg-1. The EFs ranged from 0.2 to 1.2 g kg-1 for total metals, 0.2 to 1.9 g kg-1 for total ions, 5.3 to 36.5 g kg-1 for organic carbon, and <0.015 g kg-1 for total PAHs. An assessment of the carbon mass balance demonstrated the importance of including char-bound, volatilised, and particle carbon in EF calculations. Comparatively, 76% of the metal content remained in the residue, except for zinc which was favourably released to the particle-phase. The results of this thesis contribute quantitative understanding of the magnitude and compositions of particle emissions from a range of peat fires, which can be used to improve emission inventories and inform health impact studies.