It is easy to think that all the air pollution is produced outside our houses. Unfortunately, this not true. Around our homes are many
potential pollutants. Even carpets and building materials can give off pollutants, reducing the air quality inside our homes. In some cases,
concentrations of pollutants may be much higher inside our houses than in the outside air.
What makes the situation worse is that we spend most of our time indoors (perhaps as much as 90%), at our homes or at work or school.
Many people who are old or sick cannot move very much, so they may be in their houses for 24 hours every day.
Many indoor pollutants can build up to much higher concentrations than outside. This depends on how much fresh air we can bring into the house. We need to be aware of this, because we spend a lot more time inside breathing the air in our homes, than outside.
Ventilation is Important
Scientists speak of the "ventilation rate", which is the amount of fresh air that is allowed to circulate through a house or a building in each hour. In very cold climates, houses are closed up very tightly to keep them warm, so they have very low ventilation rates.
This is great for saving energy, but is not so good for keeping the air fresh and clean. If there is not very much fresh air, some pollutants can build up to very high concentrations, simply because there is no way for them to escape from our houses.
In places like Tasmania, it will be worse in winter because people will shut all their windows and doors and put draught stoppers down to stop cold breezes.
It is best if we can have enough air coming in so that all the air is completely replaced at least once every hour. So even on the
coldest days, there should still be some small opening where air can move in and out.
Where does indoor pollution come from?
Heaters and ovens that use gas can make several types of pollutants, some of which are quite poisonous. For example, carbon monoxide or
nitrogen oxides may come from a gas stove, depending on how old it is or how it is operated.
Some modern heaters that burn gas, oil, or kerosene allow the products of combustion to stay in the house, rather than escaping
outside through a flue. They are called unvented heaters because they have no ventilation to the outside air.
They are not recommended as the
products can build up inside the home, especially if the ventilation rates are low. They also give off water vapour and so they can increase
the humidity in our homes.
In kitchens, people often use a gas stove to cook food without a rangehood fan turned on. This means that all of the products stay in the
kitchen where people are working, or children are possibly playing.
Many of the pollutants that we find inside are the same as the outside air pollution. Carbon monoxide and nitrogen oxides are two
However, there are many more chemicals and materials that we use in our homes, which can also become pollutants.
- Formaldehyde - A common chemical that may come from many laminated plastics and particle boards, and even carpets and glues that are commonly used in houses, schools, shops and offices. Some people can become very sensitive to formaldehyde and may be very sick if they are exposed to it even for short periods at low concentrations.
- Paint - Other pollutants in the home include vapours from some types of paint, that contain chemicals called solvents
that keep the paint liquid until it is applied.
- Solvents - Other solvents include methylated spirits, kerosene, and petrol. Some cleaning products give off solvents,
and sometimes ammonia. Some are kept in kitchens, bathrooms and laundries. Others are kept in the garage, but if the garage is attached
to the house, it is possible that the vapours from solvents and other chemicals could get into the air inside the house. Some paint thinners
may contain toluene and xylenes, which are part of a group of chemicals called volatile organic compounds.
Why do we worry about indoor pollution?
Just like pollution in the outside air, indoor pollution may cause problems for people, particularly if they are exposed to them for a long
time. People who are most at risk are those who are already sick, people with asthma, very young children and very old people who cannot
get out of the house and get some fresh air.
An elderly person may run an unvented heater for 24 hours a day, every day, meaning they breathe
the pollutants in all the time. Breathing nitrogen dioxide all day every day can cause bronchitis, or make it worse.
It may make young children more likely to have chronic bronchitis as they grow up, weakening their lungs. Chronic bronchitis is a type of bronchitis that can last for several years, or even a person's whole life.