Fire safety management

The integration of fire detection with building management systems (bms) and other control equipment is a complex issue. On one hand it may seem practical to have all functions involved in modern building control combined into a single system. This approach would allow the actions of non-alarm equipment such as heating and ventilation to be interdependent with those of the fire and security alarm systems. It also gives the possibility of a single, common interface.

However, a fire detection system is safety-critical, so there is an argument for it to remain independent of other equipment. After all, is it worth the risk that a fault in a lighting circuit could knock out the fire protection? Keeping the systems separate also means that users cannot mistake the visual and audible warnings of a fire for anything other than an alarm.

Complex codes

The regulations governing integration of fire systems are as complex as the concept. For a start, there are so many of them. It takes a highly accomplished system designer and installation engineer to wade through the application standards and work out which takes precedence where different systems meet.

In theory, the fire detection needs should take precedence over those of non-safety critical systems. For example, where the information from a bms and fire alarm system is channelled through a common system, all cabling must be fireproof. A simple wire connection from the fire detection system to the bms may be outside this rule. Accommodating all the implications of different codes and standards can simply make integration too complex, time-consuming and expensive.

There are also critical decisions to be made about the operational processes of an integrated system, particularly with commands. The designer and engineer must ensure that command signals do not impede the safety and security of the people the fire system is intended to protect. If a room fills with smoke, for instance, should the doors be told to open or close? Which takes priority, containment or escape?

There is no legislation on the topic of integration, only recommendations. BS5839-1: 2002, the code of practice for system design, installation, commissioning and maintenance, implies that the fire system should always stand alone. Full integration, therefore, would negate this code. However, there is no law to insist that system designers stick to the code. The Building Regulations refer to, but do not insist upon, compliance with the British Standards.

The current code of practice (BS7807: 1995) dealing specifically with integrated systems is almost ten years old and is coming under revision. A new European Standard is due for publication and the intention is to harmonise the existing standard with this. However, DD CLC/TS 50398: 2002, as its current designation indicates, is still at the discussion stage and may take around three more years before it is adopted.

Wider considerations

In addition to codes and standards relating specifically to fire detection, there are broader issues of public safety and corporate responsibility to consider. The Workplace Regulations, which state that an employer must provide a safe working environment, add a new dimension to integration.

At present there is a chance that a well engineered and designed integrated bms including a technically non-compliant fire detection element could be installed to meet the overall needs of a premises. If a fire then resulted in serious injury or death, the employer would have to prove that the fire detection was fit for purpose and working correctly despite being at odds with the recommendations in the current codes. The alternative could be a corporate manslaughter charge.

To date, there is no case in law to give a precedent in this situation. The possibility of prosecution under these circumstances is, however, very real, which may go some way to explaining why most building owners and system designers comply with the guidance documents and sacrifice true integration along the way.

Producing the goods

While regulations may appear to discourage integration, in practical terms it can be shown that some degree of interaction is necessary if safety-critical procedures are to be effective. The ability of a fire signal to tell a security system to release certain access doors as escape routes is one example. Fire detection manufacturers have responded by making products that will give some integration.

An example of simple integration is in areas such as sheltered housing, where there is a need for safety and security, but installing two completely separate systems is impractical. For these circumstances, manufacturers have developed fire detectors that can work on security system voltages (typically 12 V). This enables a single control panel and one set of wiring to be installed. A loop of the security system is then designated as a fire zone to provide adequate protection.

Making the actions of one system or component dependent on the signal from another can achieve a simple degree of integration. Again, fire detector manufacturers have responded with an array of ancillary devices and interfaces designed to enable a fire alarm signal to trigger other pieces of plant and equipment. Actions include opening and closing doors, shutting down air conditioning to prevent smoke spreading, or stopping passenger lifts safely at ground level.

Even at this level of integration, new issues can arise. Standard interface units need to have separate isolating devices fitted on either side of them to prevent a short circuit disabling part of the fire system. The installer must therefore fit three devices every time the fire system is required to interact with another piece of plant. The additional time involved could add significantly to the project time and cost.

Manufacturers have overcome this problem by developing interfaces with built-in isolators. By simplifying the installation procedure, faults attributable to human error during fitting are reduced.

Apollo’s Mains Switching Input/Output Unit, for instance, achieves this because it is loop powered, therefore does not require a separate power supply or slave relays, simplifying and speeding up the fixing process. This particular interface can receive information from devices (inputs) and operate equipment (outputs).

Good communication

Ultimately, the question of integration is a matter of communication. The benefits of having diverse building products and systems co-operating with each other are self-evident. Faster response times, co-ordinated strategies in case of emergency or failure, pre-planned and pre-programmed evacuation procedures to name a few. In the end, it becomes a question of how we achieve integration.

Originally, it was thought that a single, unified system could cope with all the demands of modern building control. In practice, total integration has proved impractical and brings a number of unacceptable risks, including the possibility of compromising safety-critical functions. Instead, the practical and regulatory pressures have produced another possibility: keep each system separate, but integrate communications. The advent of internet computer technology has gone a long way to making this solution a reality.

Essentially, it has led to the development of an integrated network that provides a platform for the management and control of a building. This provides a communications platform that enables all the different elements of the building to co-operate fully while retaining each system’s integrity.

The shift in emphasis from system to information integration brings a number of benefits. It provides the user with a familiar interface: typically a computer or graphics display. More importantly, it enables the different system manufacturers to concentrate on the evolution of features that are most needed in their particular field without having to worry about the potential impact on the functioning of other parts of the bms.

The same principle applies to maintenance of such a system: if a valve needs upgrading on the hvac system, say, it can be achieved by an engineer in that field. The change cannot adversely affect the functioning of any other system because the systems are still essentially separate. Equally, it will not affect the way in which the hvac system responds to signals from other equipment and vice versa, because the information network controls what response will be made.

The question of maintenance also raises lifetime costs. In a fully integrated system, if the protocol becomes obsolete or the manufacturer withdraws some components from production, the user could be faced with replacement of the entire bms. Where individual systems remain but only the communications is shared, there is far less risk that obsolescence in one system can affect the entire network.

The attempt to integrate all building control equipment onto a single system was a false dawn. The issues involved, both regulatory and practical, are simply too complex. In addition, the benefits are outweighed by issues of cost, in-built obsolescence and risk to life-critical functions.

A common communications platform offers the benefits of integration while removing most of the risks. It is hoped that the proposed new regulation on the integration of fire detection and alarm systems will take these points into account and provide the industry with a regulatory framework that encourages continued but responsible development.