Do masks do the job?

They have become the most recognisable image of the Sars crisis. From the Far East to Toronto thousands won't venture on to the streets without wearing a face mask. Even in Britain, where the virus has yet to take a hold, a new website has sold 10,000 Sars masks in the past two-and-a-half weeks. But do any face masks - whether they are designed to stop the spread of a virus, or simply to protect the DIY brigade from building dust, or cyclists from car fumes - actually do the job?

Dr Michael Apple, author of the Hamlyn Family Encyclopedia of Health, says that the many masks on the market are effective for different purposes - and to varying degrees: "But none of them should be relied upon to protect you against Sars in a high-risk environment.

"The other way you can catch Sars is by touching and eating things which have been in direct contact with the virus. The best advice is to follow normal cleanliness, with lots of hand-washing, and avoid handling things that could be contaminated."

We asked the experts to comment on the various face masks being marketed in Britain.

Surgical face mask, from Boots, £3.69. Made from viscose and polypropylene, they are used mainly in hospitals to capture micro-organisms in the breath of medical staff to protect the patient against infection. They protect those around the wearer, rather than the wearer. Dr Apple says: "I have known parents caring for premature babies at home who wear these masks if either of them catches a cold or flu. The masks reduce the risk of passing on bugs through sneezes, sniffles and coughs."

Techno Anti-Pollution Cycle Mask, £29.99, from Cyclecare in Kensington. Made from neoprene, a material used in wetsuits, this is designed for city cyclists with a carbon filter to protect against car fuel pollutants such as lead oxide, sulphur dioxide and benzene.

There is a second layer in the filter to stop inhalation of the tiny particles in dust, black smoke, diesel particulates and nuisance pollens. Tom Bogdanowicz, from the London Cycling Campaign, says: "Cycle masks don't offer much protection from pollution, although they do filter some of particles. Choose the ones made from neoprene, as they fit much better than others.

A recent study showed that London car drivers are exposed to more pollution inside their cars than cyclists are on the road." And, a cautionary note from Dr John Harvey, a lung specialist and member of the British Thoracic Society, who says: "These won't keep out gases such as ozone or lead fumes."

The Air-Aid Mask, £4.99, from www.safetymasks.co.uk. Made from a synthetic fabric with a charcoal-activated filter. A lightweight mask to be used for basic protection in emergency situations, such as a chemical attack, or to stop smoke inhalation - but it won't protect against carbon monoxide.

It can also be worn as protection when using household cleaning products, spraying in the garden, or painting. Dr Apple says: "This will probably do what it claims. It will offer some protection in the short term."

3M Foldable Respirator, £9.99, from www.safetymasks. co.uk. This has a filter made from a web of polyester fibre, polypropylene, with an exhalation valve to keep the wearer cool. Offers protection against Sars. It cannot be worn by men with beards or other facial hair that may prevent the mask fitting the face snugly.

Dr Harvey says: "This mask is very good. After gases, bacteria are the next hardest thing to keep out. The Department of Health recommends the pink duck-billed masks made by Universal Hospital Supplies.

"They are tight and not very comfortable, but I trust them - I use them when I deal with TB cases."

Duram NBC Personal Escape Mask, £69.99, from www.safetymasks.co.uk. Made from rubber, this is designed to be effective in the event of a chemical or biological incident. It protects the respiratory system and the eyes against toxins. It has no adjustment straps, but is pulled over the head like a Balaclava.

Dr Apple says: "This mask is the most effective of all the options. One of the ways people catch Sars is through tiny droplets, and because this mask covers your mouth and nose, the risk would be significantly reduced."