Indoor pollution majorly refers to air & noise pollution. Following are the main causes of indoor pollution.

1. Pollutants are also found indoors from infiltration of polluted outside air and from various chemicals used or produced inside buildings. Both indoor and outdoor air pollution are equally harmful.
2. Indoor air pollution occurs due to the use of fuel wood, waste material, coal, etc. in ‘chulas’. Indoor smoke arising from ‘Chulas’ is a major issue in rural India. Thousands of women and children die yearly due to it.
3. ‘Second hand smoke’ i.e. tobacco smoke affecting other people apart from active smoker is also a major indoor pollutant.
4. Molds & other biological particulate substances like plant pollen & animal dander.
5. Volatile Organic Compounds (VOCs) arising from paints, lacquers, thinners, pesticides, whiteners, glues etc. are found in much higher concentration indoors than outdoors.
6. Loudly played radio or music systems, and other electronic gadgets can contribute to indoor noise pollution.

Definition-: Indoor pollution refers to chemical, biological and physical contamination of indoor environment due to particulate matter (pm) such as tiny particles of dust and dirt in the air that include soot and dust mites and gases like carbon monoxide, nitrogen oxide, and sulphur dioxide.

The major causes of indoor air pollution are as follows:
1)Heating and cooking indoors:- Burning wood and coal in a stove or on an open fire releases particulate matter (PM). Heating and cooking with gas releases tiny particles of nitrogen dioxide (NO2) and carbon monoxide (CO) into the air you breathe. This is very harmful for small children, whose lungs are developing, and for people with asthma and lung problems

2)Damp and mould growth:- Damp leads to condensation, which encourages mould and other fungi to grow. Lots of things can cause this, from cooking, to washing and drying clothes. If your home’s damp, you might have an irritated nose and throat, or feel short of breath. If you have a lung condition, your symptoms may get worse. It’s common to have an allergy to mould.

3)Smoke and Vapour:- If anyone smokes in a house, tiny particles from tobacco smoke can drift all through the house. These particles can remain at harmful levels for up to five hours. Breathing in this smoke may cause your nose or throat to get irritated, and one might cough or have trouble breathing. Candles and incense sticks emit particles and other pollutants when they burn which also cause pollution.

4)Chemicals used in cleaning and decorating products:- The products we use to clean and decorate our homes can sometimes contain chemicals called volatile organic compounds (VOCs).Products containing VOCs, particularly those in a spray, can cause irritation to your lungs and may increase your risks of developing an allergy or asthma.

5)Building Materials:- Building materials such as asbestos, fibreglass, VOCs(VOCs in building materials may include roofing and flooring materials, insulation, cement, coating materials, heating equipment, soundproofing, plastics, glue and plywood.) and radon(Radon is a natural radioactive gas that comes from rocks and soil in granite areas.) leads to indoor pollution and thus pose a risk to your health