# Particulate Matter During Food Preparation on a Barbecue: A Case Study of an Electric Barbecue
## 3 Results and Discussion  
As shown in Figure 3, the ternary plot shows the fractional contributions of the different PM fractions. The figure shows PM\({}_{1}\) (submicron particles), PM\({}_{4-1}\) (particles between 1 and 4 \(\upmu\)m), and PM\({}_{100-4}\) (particles between 4 and 100 \(\upmu\)m) for three environments: grilling point (denoted grill), indoor of the adjacent flat (indoor), and background. An examination of the grill data (represented by the blue dots in Figure 3) shows that they are distributed mainly along the grid lines of the PM\({}_{4-1}\) axis, with a slight tilt towards the 100% PM\({}_{1}\) vertex. This suggests that the particles generated by the grilling process  
Figure 1: The location of sampling sites presented on the OpenStreetMap background [44], a map created using QGIS 3.22 Bialowieża [56]. Figure 2: Scheme of sampling sites at two flats. On the balcony in the left flat there is a grill with the AQ Guard while in the second flat, completely separate, there is an opened window with the AQ Guard inside. are predominantly composed of fine submicron particles. The generation of submicron particles (PM\({}_{1}\)) is often associated with high-temperature processes, including combustion, heating, and even food-related emissions such as fat evaporation [3; 6; 57]. Our study used an electric grill (which does not involve direct fuel combustion), but grilling still involves high temperatures that generate fine particles through processes such as fat evaporation. When fats and oils from food reach high temperatures, they can vaporise. Upon cooling, these vapours condense into submicron aerosols, significantly increasing the proportion of PM\({}_{1}\)[58; 59; 60]. This effect is further enhanced by the high power of electric grills (round 2000 watts), which rapidly heats fats and oils, thereby accelerating the production of ultrafine particles. This is consistent with the finding that PM\({}_{1}\) can account for over 90% of the total particle mass during grilling. It is noteworthy that a study by [PERSON] et al. (2022) [6], in which the researchers used a charcoal grill, found that PM\({}_{2.5}\) accounted for 97-99% of PM\({}_{10}\). In addition, PM\({}_{1}\) accounted for 98-99% of PM\({}_{2.5}\), indicating that the majority of particulate emissions from charcoal grilling are very small, submicron particles. This suggests that submicron particles remain a concern, even with electric barbecues. Another process that can potentially affect the concentration of submicron particles is the presence of cooking by-products. In addition, particulate matter can result from the emission of small solid particles from food surfaces, including charred or burnt particles that are extremely fine [61]. The reasons for the reduction in PM\({}_{4-1}\) and PM\({}_{100-4}\) near the grill can be observed. Larger particles (PM\({}_{4-1}\) and PM\({}_{100-4}\)) are typically generated by mechanical processes, such as the production of dust, dirt or larger combustion particles in traditional fuel-based barbecues [13; 62]. In the case of the electric barbecue, the absence of combustion of fuels such as charcoal reduces mechanical disturbance and the generation of particulate matter from these sources. The absence of traditional combustion also explains the lower concentration of coarser particles (PM\({}_{100-4}\)), as there is no burning fuel to produce ash or large particles. The slight shift of the blue data points (representing barbecue emissions) towards the PM\({}_{100-4}\) axis can be attributed to the influence of background particles present on the balcony. Although the barbecue emits mainly fine particles (PM\({}_{1}\)), some coarser background particles (in the PM\({}_{100-4}\) range) from the surrounding outdoor environment, such as dust, pollen or urban pollution, may mix with the barbecue emissions [63]. Indoor air, represented by the orange data points in Figure 3, is reflected in the more evenly distributed PM\({}_{1}\) fraction.