THE decor in the offices of Dashiell Hammett's private detective, Sam Spade, memorably consisted of only two desks, a filing cabinet and an attitude, but increasingly professional standards require businesses to put more thought than ever before into the interior design of their offices.

From the selection of chairs to the use of light, good office design has become a crucial matter to ensure satisfaction among both customers and employees.

"It's a professional attitude and more and more these days, high standards are expected," says Cathal O'Byrne of Sisk Contract Interiors Limited. "The introduction of ISO 9000 in particular has helped to increase awareness of high standards."

Sisk is a big player in the office furniture market, with much of its business coming through architects, although the company also accepts approaches directly from clients. The company offers services from the selection of desks and chairs to "turn-key" projects, where it takes responsibility for everything from the type of carpet used to the artwork on walls.

"As design develops and with, so many factors involved now, architects and designers are leanings more towards the use of companies like ourselves to keep in touch with all that's going on, says Cathal O'Byrne. "We are there to advise them, to help them to decide which system would best suit the client's needs."

Sisk are main agents for Haworth, the huge US office furniture suppliers. Haworth's development is a history of office design in miniature, from the panel-based systems developed in the 1970s (and still common in most offices), through advances in creating central arteries or beams to which panelled units could be added or taken away without disturbing other users, and finally on to the mobile office systems exemplified by the "Crossings" system, where each unit, from the desk to the computer trolley, is fully mobile.

Factors to be considered in the office design include storage requirements, the height of panelling, the use of light and, with the proliferation of computers and faxes, cable management - there is little point in investing in expensive office furniture if customers and staff risk damaging equipment or themselves because of stray wiring.

The increasing prevalence of computer-aided design (CAD) has speeded-up many aspects of the design process, as well as allowing designers to interface with facilities managers in large companies. CAD is fast approaching the stage where designs can be transmitted by modem as readily as by fax, allowing the client to have input to the design at all stages.

"The beauty of CAD as opposed to the old drawing board aspect is that it is a lot easier to turn around design elements at a faster rate and adapt to any particular requirements needed," says Cathal O'Byrne.

The trend is still towards open-plan offices, although where confidentiality is required, cellular offices are still a necessity. The introduction of an open-plan office system can create difficulties, though, particularly for those who are used to the enclosure and privacy offered by cellular systems.

"There were groups in the past who were used to their own cellular offices," says Cathal O'Byrne. "To suddenly move such people out into the open is something of a culture shock for them, so it can be a difficult aspect with which to cope.

Inevitably, the cost of designing a new office varies. The difference in price between a cluster of four work stations can vary by several thousand pounds depending on the type of material used and the purposes for which they are required.

Even selecting a chair is not a simple matter, with ergonomic factors, such as the adjustability of height, back-rest and arms, to be taken into account. The difference in price between a standard office chair and a top-of-the-line, ergonomically-designed model could be as much as 40 per cent.

The benefits to be gained from consulting a professional design firm are, in the end, considerable. "The client and the architect are benefiting in two respects," says Cathal O'Byrne. "They are getting a quality product and it is being offered to them on the understanding that this will cover all their particular needs, because we know from experience the problems that can occur."