Figure 2.

${\mathrm{PM}}_{2.5}$ and CO box plots of daily mean kitchen area exposure concentrations at each follow-up visit (baseline, 3-, 6-, 12-, 18-, and 24-months) for LPG stove intervention participants (LPG) and control participants (Control). Daily mean metric used is defined as the mean of the two consecutive 24-h average concentrations, where available. During the second year (follow-up visits:18- and 24 months) the control participants received the LPG stove intervention and vouchers for 1-y supply of free fuel and intervention participants stopped receiving free fuel but kept the LPG stove. Interquartile ranges of the box plots represent the 25th and the 75th percentiles of the daily means for each group; the middle line of the box represents the 50th percentile. Numeric data is provided in Table 2. Note: CO, carbon monoxide; LPG, liquefied petroleum gas; ${\mathrm{PM}}_{2.5}$, fine particulate matter with aerodynamic diameter of $\le 2.5\mathrm{\mu }\mathrm{m}$; WHO 24-h guideline, World Health Organization daily guideline (${\mathrm{PM}}_{2.5}$: $25{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$, CO: $9.4\text{\hspace{0.17em}ppm}$).