Hot stuff prompts cover up by drivers.

Racing drivers have long been considered hot stuff but, with fire an ever present spectre in the sport, that is one thing they don't want to be...

In days gone by, overalls were simply worn to keep the driver's clothes clean, and the only means of discovering the fire-retardant property of various fabrics was to cover parts of the body, set fire to it and see what happened!

Fortunately technological advancements now negate the need for such brutal tests, and the FIA has stringent international guidelines for head-to-foot protective clothing that allows competitors to walk away, virtually unscathed, from even the most horrifying blaze.

Working with their respective racewear manufacturers, many of the crews driving in this year's Le Mans 24 Hours can compete at the highest echelon of their sport safe in the knowledge that, in the unlikely event of a fire, they have the best possible protection.

Skin is as vital a body organ as the heart, liver or kidneys - put simply: without enough of it, we die. Burns destroy skin. The temperature of the tissues just under the skin surface, in comfortable conditions, is within a few degrees of 33 Centigrade. Exhaustive research, which started as early as 1947, has related the degree of injury to the temperature to which the skin is elevated. If this temperature is raised to only 45 degrees Centigrade, burns are initiated and, as the temperature is raised further above this critical level, so does the rate of tissue damage. Damage does not stop when the body is withdrawn from the heat either, but when the tissue temperature has dropped to below 45 degrees.

In sportscar, drivers must wear gloves, balaclava, socks, shoes and homologated overalls that comply with the FIA 1986 Standard. It is also recommended they wear fireproof underwear that complies with the same standard. Ingeniously, drivers of single-seater cars in races with standing starts are required to wear gloves of a high-visibility colour that contrasts to the predominant colour of the car to clearly draw attention their to the race starter in the event of any difficulties. This is not the case at Le Mans, as the race starts with a rolling getaway, and most of the driver will race with a colour scheme that best fits in with the team's sponsors.

The FIA 1986 Standard for heat and flame-resistant clothing for competition drivers, including the revision of January 1987, stipulates that overalls must cover the whole body extending to cover the neck, wrists and ankles. Large toothed metal zips must have flame-resistant backing tape and covering flaps made of the same fabric, and any 'Velcro' type fasteners must also be made in the same flame-resistant material.

FIA-approved testing houses, of which there are nine worldwide, set rigorous standards and garments must be accompanied by certification that each of its fabrics has been tested to the ISO 6940 Standard, a basic flammability test. The specimen is then subjected to the ISO test method for 'protective clothing against flames' before receiving its homologation.

Samples are held in an 800C liquid propane flame and have to meet or exceed the minimum requirement of 12secs to record second-degree burns, which reflects, approximately, the escape time for the driver. Yet more sophisticated is 'Thermo Man' ((TM)), a highly complex life-size dummy equipped with 122 electronic sensors used to simulate burn patterns. This advanced and complex experimentation equipment is unique to Du Pont, the producers of the Nomex(R) and Deltac fabrics used to make the majority of competition overalls.

Given the right conditions virtually anything will burn, but the aim of racewear manufacturers is to create a material that resists destruction by flame. Certain materials are inherently resistant to flame but, for various reasons, are totally impractical to be made into clothing. Nomex(R) is unique. It is a modified nylon able to withstand much higher temperatures than other man-made fibres, breaking down at over 370 degrees Centigrade. Research showed however that a single layer of Nomex(R) would not prevent critical burn injury so, by adding layers - of which three are now standard - the transfer of heat to the body is dramatically reduced. The quilting effect and the air cushions it creates, along with flame resistant underwear, help stop the heat of a fire getting through to the body.

With the addition of a balaclava, gloves, socks and shoes, the driver is well protected. He is not, however, fireproof, but the industry standard protective clothing will dramatically increase his chances of survival during the critical time of escape.

Each driver has his own specification of overalls customised to meet the exacting demands of the job. Each basic suit, without any sponsors' logos, takes four hours to make but, start adding complicated logos, and this alone can add 12 hours of millimetre accurate sewing to each set of overalls.

Drivers are constantly demanding thinner, lighter suits to cope with cockpit temperatures, which can top 50 degrees Centigrade in some of the hotter countries where sportscar racers compete. Different materials have been tried, but the combination of its fire protection qualities and light weight, currently make Nomex(R) an unbeatable solution.