Walking home along the polluted city streets, you could be forgiven for thinking of your home as a sanctuary from the fumes.

But when you get indoors you could be breathing in just as much pollution as you were outside.

And it could be causing you as much, if not more, harm.

Added to the background pollution that drifts indoors are the fumes from your carpets, furniture, gas appliances, air fresheners, polishes and cleaning fluids.

For the air inside your home is a cocktail of chemicals about which nobody knows very much.

Tim Brown, deputy secretary of the Brighton-based National Society for Clean Air, said: "The Government says stay indoors if there is an air pollution problem. But it is probably worse indoors than it is outside."

There are biological problems peculiar to our modern centrally-heated and tightly air-sealed homes.

Dust mites and other tiny creepy-crawlies often thrive in warm, dry conditions, possibly aggravating asthma and other allergies.

Chipboard can release formaldehyde and gas ovens produce high levels of Nox, a mixture of nitrogen dioxide and nitric oxide - often at levels high enough to spark pollution warnings if it was found outdoors.

The glues and dyes used in modern carpets and furniture give off a whole range of volatile organic compounds, known as VOCs in the trade.

The same compounds are found in man-made waxes, polishes and air-fresheners.

The smell in air-fresheners comes typically from one of them, limonene.

As with outdoor air pollution, the potential effects of long-term exposure worry researchers.

Mr Brown said: "There has not been a lot of work done on whether it is a danger but people with asthma, for example, should take precautions.

He said the Government should pin down what, if any, the health effects are of pollution in the home and people should be given advice about how they could minimise the risk.

He said: "It is difficult to point to really strong evidence of health effects, except in susceptible people. They might find themselves aggravating existing conditions.

"Nobody knows whether these VOCs, for example, are dangerous. They probably are not but they may trigger allergic reactions in some people. There is a big dispute whether they just make you feel a bit queasy or if they are carcinogenic.

"The interesting thing is, people get very upset about outdoor air pollution but are much less likely to do something about it in their own home.

"There are regulations covering the workplace. We have got objectives for outdoor air quality. The missing piece of the jigsaw is indoors."

One person who has tried to cut down the amount of pollution he is exposed to at home is Clive Pepe.

His house, in Carlyle Street, Brighton, is mostly carpet-free, using wood and lino floor coverings to reduce the risk.

There are other environmental benefits of this too. The wood used on the floors was recycled from a theatre in Eastbourne, while the lino is made from linseed rather than a man-made substance.

Mr Pepe, a trained microbiologist, said: "It is pretty well known that carpets are a massive sink for dust mites and this is a very big contributor for allergies and trigger for asthma."

He has kept some carpet, to absorb any pollution that remains. He said: "The danger is you have got all this stuff moving around so I have got carpets on my stairs and the plan is to change it every four years."

Old furniture went as well, to be replaced by beds, tables and chairs that used wood rather than chipboard and, just as importantly, the paints and treatments were natural not synthetic.

Mr Pepe said: "It is the slow, long-term release of compounds, particularly glues, but there are a lot of other things that you cut out.

"There has been very little study done of the individual chemicals, let alone in combination.

"You are never going to produce the perfect house. The goal was to do it on a budget affordable to the average person."

The Government has so far been wary of studying whether or not all this pollution is bad for us, with various departments playing pass the parcel as they try to avoid responsibility. It has ended at the Department of Health's door.

Kemp Town MP Des Turner said manufacturers could design out some of the problem substances if it was proved they posed a risk.

He said: "I doubt whether anybody really knows just how genuine a problem air quality in the home is.

"Some agency needs to take it upon itself to look at whatever evidence is currently available and try to get a hand on the size of the problem, if indeed it is a problem."