BRE DG513 PDF

INTRODUCTION AND BACKGROUND

Fire protection is an essential element of buildings and aims to minimise the harmful and costly impact of fire by various means, including smoke detection, fire compartmentation, manual fire-fighting and fire suppression systems. For many buildings, especially those of high value, fire suppression systems are invaluable because they can control and in some cases extinguish a fire. Fire suppression options include sprinkler, watermist and gas extinguishing systems: each operates differently and has different applications.

Gas extinguishing systems are particularly suitable when rapid fire extinguishment is required (rather than progressive fire suppression by a sprinkler or watermist) and when minimal deposition of extinguishing media is desirable (rather than the potential water damage associated with a sprinkler or watermist).

Gas extinguishing systems are complex engineered systems that require specialist understanding and support. They are usually used only in areas that are normally unoccupied or in occupied areas where staff are appropriately trained. They are generally not selected to protect whole buildings. These systems are not employed for the protection of life.

The decision to use a gas system is normally based on the building user's or insurer's consideration of business continuity for essential processes, equipment or information, or for irreplaceable items or facilities. Typical applications are: computer rooms, electronic data processing facilities, communications equipment, clean rooms, control areas, record stores, cultural heritage premises, machinery spaces, plant enclosures and flammable liquid stores.

The fire protection objectives of a gas extinguishing system are to:

• extinguish fire
• limit the spread of fire and fire damage
• limit the production of smoke
• prevent re-ignition of the fuel for a specific period without intervention by trained personnel
• limit the interruption to vital equipment and business processes
• reinstate the building and contents quickly after a fire.

Gas extinguishing systems have been used for over 100 years. Historically, in fixed systems, halon and carbon dioxide were the gases primarily employed. Halon is a versatile fire extinguishing gas which is both efficient at extinguishing fire and suitable for use in occupied areas. Carbon dioxide also extinguishes fires effectively but only at toxic concentrations and as such has restricted use. 

Halon has an ozone depleting potential and, under EC Regulation 2037/2000 and Statutory Instrument 528/2002, its sale or use as a fire protection system has been phased out, with a few (mainly military) exceptions.

Since the early 1990s, replacements for halon (often referred to as ‘halon alternatives' or ‘clean agents') have become available and so the use of other gas extinguishing systems has increased. Associated with the development of new gases has been the introduction of standards and approval schemes.

The effectiveness of fixed gas extinguishing systems for industrial and commercial applications has been demonstrated over many years but research and development is still being actively pursued in several areas.