Electrical Contracting News (ECN) May 2016 - Page 42

SPECIAL FEATURE FIRE DETECTION & SECURITY MAKING SENSE OF FIRE DETECTION Jeremy Roberts at SONA discusses how sensing technology used and trusted by over 90 per cent of the UK Fire and Rescue Service is helping drive the mains smoke alarm market towards a simplified alternative. S ince legislation came into force in England requiring private landlords to install smoke alarms on every storey of their rented properties, it has never been more prevalent to ensure the correct alarm is used to protect properties and tenants. However, traditional solutions, such as ionisation and optical smoke alarms, offer contrasting benefits that can make correct specification confusing and difficult. Call outs The UK Fire and Rescue Services are called out to approximately 50,000 domestic fires per annum, leading to almost 500 deaths and 11,000 injuries. From these statistics it’s quite simple to see the importance of smoke alarms, meaning correct selection is absolutely essential. The two most common types of domestic smoke alarms used throughout UK housing stock are ionisation and optical, both using different methods of detection. Ionisation Historically, ionisation smoke alarms have been the most popular. The smoke alarm has a small amount of radioactive material between two electrically charged plates, which ionises the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the flow of current and activating the alarm. Although ionisation smoke alarms are very sensitive to small particles of smoke produced by fast flaming fires, such as chip pan fires, they do have a tendency to generate a large number of nuisance alarms, mostly from toasters, which can lead to end users removing the battery or completely removing the smoke alarm. 42 42-43 FD&S – Sprue.indd 42 11/04/2016 14:28