If the units are inside the building the code calls for automatic fire detection and sprinkler systems to be considered.Internally, furniture must comply with the latest domestic regulations, waste bins must be of metal and fitted with lids and smoking must be banned in corridors.The draft code of the insurers is likely to come into effect more quickly than either the revised standards of the BSI or HSE.These two bodies are trying to harmonise their codes with one another, and with a European Community directive that has yet to go before the Council of Ministers. Neither can draw up regulations until the final version of this directive is known.Just how the insurers will enforce the code when it is finally agreed will be up to individual insurance companies.But Mr Lewis points to the example of Sweden where up to 30 per cent of a claim can be withheld if recommended working practices are not followed.In Britain it is less easy to generalise about what insurance companies will do to encourage the use of secure and fire resistant portable buildings.Recently Rab MacDonald, the marketing manager for Conway Products, claimed that insurance companies were considering whether to reward users with lower premiums or punish non-users by increasing the excess.Conway markets an anti-vandal cabin, the Rhino, that competes with products from BTH, a specialist in secure units. One of BTH's customers, Hall Brothers Electrical, can already demonstrate benefits from using secure units. In the seven years the company has used them, there have only been three break-ins, all of which needed torch-cutting equipment.Jack Clayton, finance director at Hall Brothers, said: 'Premiums are less because we have secure units, but this is not because the insurance company recognises the secure units. It is because our claims have gone down over the years so the premiums have been reduced.'Both BTH and Conway recognise that the greatest threat of fire is from arson, because the other big threat, from electrical fittings inside the building, has been tackled.Most portable buildings incorporate miniature circuit breakers, as recommended in the IEE 15th Edition, which are safer and quicker to respond than rewirable fuses. Units are also installed with an earth leakage trip.The latest anti-intruder features include full-length hinges and anti-jemmy angles on doors, heavy duty window shutters, and galvanised steel walls, ceilings and floor. Units with these features are available from many manufacturers - but at a price.Maurice Sellers, sales and marketing manager with BTH, said: 'Prices vary a lot, but roughly you would pay between 10 and 12 per cent more for a steel secure unit than a timber equivalent.'Not only the insurers but the HSE and the BSI are preparing to incorporate many of these security and safety features into their codes of practice. So the construction industry must prepare itself to pay more for its site accommodation - the extra investment could well pay for itself in reduced losses and premiums.