Burning solid fuels like coal indoors, especially in poorly ventilated spaces (common in traditional cooking or heating practices), releases a complex mixture of pollutants including high levels of particulate matter (PM2.5 and PM10), carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen oxides (NOx), polycyclic aromatic hydrocarbons (PAHs), and heavy metals. These pollutants cause significant indoor air pollution and pose serious health risks.