AFTER five years in the Army, Hugh Bell knows the importance of being prepared.

As soon as his mail order package arrives, he is going to hand out the contents to his nearest and dearest. A bulk order of 15 gas masks may seem excessive, but Hugh is taking no chances.

"I understand what a chemical or biological attack can be like, theoretically," he says. "As a result of what happened in the States on September 11, it is clear there are no morals attached to these terrorists.

"It is not so much that it is likely to happen but, if it does, I would not be surprised and I would rather be prepared. In the Army you are trained to be prepared; preparation can save you, rather than reacting afterwards, when it will probably be too late. It is not being worried, it is about being prepared."

Hugh was one of dozens of people who called Genuine Army Surplus in Darlington yesterday, on the hunt for gas masks. Steve Thompson, who runs the store, reckons he has sold about 200 since the weekend, along with 200 NBC suits, designed, as their name suggests, to give protection from nuclear, biological and chemical attacks.

"The only time I sold gas masks before was to collectors, or to certain people who like to wear a gas mask, so we had built up a bit of a surplus, but over the weekend it went daft," he says.

"Most people are not scared for themselves, it is more for their children and grandchildren. If someone came at your child with a stick, you would get the man with the stick, but this is the unseen element. People want to protect their children."

The masks he sells are S10 respirators, standard British Army issue. The NBC suits are the same as those issued for troops during the Gulf War. But Steve is uneasy over the sudden leap in demand, so much so that he says he will cut the price of masks, which were £35, and suits, which were £20. "I've tried to put people off, but if people want to buy them I will sell them cheaper, to get rid of them. I personally think the risk is minute, but people are scared because they don't know enough about the situation to make an informed decision," he says.

"But I'm not happy about selling them for that purpose. It is alright if they want it for the bedroom or playing around with, but people are watching the news and getting scared. The terrorists want to scare us and it is working."

Steve's experience has been replicated across the country, as Army surplus stores report a surge in demand for gas masks and protective suits. From Dorset to Edinburgh, shopkeepers are opening the boxes they thought would be gathering dust for years.

The World Health Organisation yesterday joined in the frenzy, urging governments to quicken preparations for possible germ warfare. Last week, the United States grounded crop-dusting planes, for fear they could be used to spread lethal chemical or biological agents.

But protective suits and gas masks will be of little use if Osama bin Laden did turn to chemical or biological weapons, says Malcolm Hooper, professor of medicinal chemistry at Sunderland University.

"I don't think there is any realistic means of defence for the civilian population. You would have to wear a gas mask all the time, you would need detectors for biological weapons - you would have to treat the country like a battlefield. NBC suits don't represent a realistic way of addressing the situation," he says.

Chemical weapons, such as Sarin, VX and Soman, largely work by attacking the enzyme which controls respiration, so stopping the victim from breathing. Sarin was used to deadly effect by a religious cult on the Tokyo underground six years ago, when 12 people died and thousands more were injured.

"There isn't really an effective protection that anyone can take against these things," says Prof Hooper. "There is no way you can defend yourself against somebody releasing a nerve agent on somewhere like the Newcastle Metro. You normally breathe it in, but it can also be absorbed through the skin.

"There are chemical alarms which can detect these things, but Soman does for you in about five minutes. Most people would see nerve agents like this as some of the most dangerous."

Along with these, there are also blister agents, such as hydrogen cyanide, which can be easily manufactured and is in common use to destroy wasps' nests. These agents also stop the victim from breathing and were used during the First World War. This group also includes mustard agents, used by Saddam Hussein against the Kurds in Iraq.

"They are fatal if the levels are high enough but, for nerve agents, it is only a few microgrammes," says Prof Hooper. "You have got to spread them around and there are various ways of doing this. That is the advantage of Scud missiles, in that there is an explosion that pushes this stuff out into the air.

"Inhalation is a very fast route of getting this into the bloodstream, it is almost as quick as an injection. Skin absorption is slower, and absorption through food or water is slower still."

Biological warfare covers fungal, plant and animal-derived toxins, which largely work by disrupting basic functions, preventing the body from handling oxygen and killing the victim. This includes poisons such as ricin and anthrax, as well as smallpox and Ebola viruses.

"The list is endless. If you are hell-bent on destroying people by poisoning them, there are lots of things you can do," says Prof Hooper. "Anthrax spores are readily harvested, and if they were turned into an aerosol and breathed in, that would represent a serious infection of anthrax.

"It causes damage to the membrane of the lung and to the nerve system as well, although you can treat it if you get antibiotics quickly enough. The level of technical sophistication to produce sufficient quantities varies for each one.

"Unless you are dealing with very well equipped laboratories which are capable of manufacturing these biological materials on a sufficient scale, which would not be easy, you would be looking at mainly a chemical threat rather than a biological one.

"Chemical weapons can be made by much smaller groups, as we know from the drugs trade. People are making drugs in their garages and the same could happen with chemical weapons."

For Hugh Bell, as he prepares to equip his mother, brother, sister, nephews and nieces with gas masks, the attacks on the World Trade Centre and the Pentagon have shattered the assumptions we make about our safety. "That day has changed how we should look at terrorist attacks," he says. "We were all surprised two weeks ago, we cannot be surprised any more."

But for Prof Hooper, the solution is not to don a gas mask and protective suit. Instead, it has to be to make the world a safer place. "There is very little we can do to protect the civilian population against these sort of attacks," he says. "Chemical warfare would be just as lethal as flying those jets into the twin towers."