Indoor air pollution is often influenced by activities and materials within enclosed spaces. Because indoor environments are more confined, pollutants can accumulate quickly if not properly ventilated. 

Common indoor sources include: 

• Cooking and heating – especially when using gas, wood, or other fuels  

• Tobacco smoke – a major source of indoor particulate matter and toxic compounds  

• Building materials and furniture – can emit volatile organic compounds (VOCs), especially when new  

• Cleaning products and chemicals – release VOCs and other airborne substances  

• Candles and incense – generate particulate matter and other pollutants  

• Moisture and biological sources – mould, dust mites, and bacteria thrive in high humidity conditions  

• Outdoor air infiltration – pollutants from outside can enter indoor spaces through ventilation or open windows

Without adequate ventilation, indoor pollutant levels can become higher than those outdoors, highlighting the importance of monitoring and managing indoor air quality.