Tackling a deadly enemy: smoke ventilation with AOV rooflights

David Brown of daylighting & ventilation specialist Lareine Engineering, looks at the role of Automatic Opening Vent (AOV) rooflights in today’s Smoke and Heat Exhaust Ventilation Systems – and the factors governing their specification.

It’s widely known that the majority of deaths resulting from building fires are caused by inhalation of gas, smoke or toxic fumes. Today’s Smoke and Heat Exhaust Ventilation (SHEV) systems are designed to address this fact, by assisting with the extraction of smoke and fumes from burning buildings.

Correctly designed smoke ventilation systems keep escape routes free from smoke and assist fire-fighting operations by creating a smoke free layer. Automatic Opening Vents (AOVs) can play a key role in these systems.

AOV designs

A variety of AOV designs are available, AOV rooflights & modular rooflights being a popular choice – combining the ventilation aspect with the provision of natural daylight. Typically, a modular AOV will consist of a base unit with a glazed lid section that is hinged and forced open when required, by an actuator linked to separate AOV controls.

AOV rooflights are typically installed over atriums, corridors or stairwells and are frequently specified in hospitals, schools, hotels or apartment blocks.

Architectural window ventilators and glazed louvre ventilators are available for facade applications. AOV roof escape hatches and other designs which do not feature any element of glazing, are also available for areas where daylighting is not a requirement.

Irrespective of design, construction or siting, all AOVs are subject to the same regulatory requirements.

Specifying compliant AOVs

When specifying AOVs, it is vital to ensure maximum safety and compliance with Building Regulations.

Although standard automated opening rooflights can aid smoke clearance, they should never be used specifically

AOVs are available in a wide range of configurations.

To comply with UK Construction Product and Building Regulations, purpose built AOV units must be specified – and these must be CE marked against BS EN 12101-2:2017. This is the European Standard which covers the appropriate joint testing methods for components specifically installed as a natural smoke and heat exhaust system.

The UK’s current EN12101-2 regulatory compliance actually became enforcible in 2006, but was not really enforced until the Construction Products Directive changed to the CPR in July 2013, making joint testing of AOV units and actuators to BS EN 12101-2 absolutely compulsory.

Prior to 2006, it had been possible for actuators and AOVs to be tested separately and assembled on-site.

In some cases, untested actuators were fitted as part of the overall assembly and this resulted in the final installations being passed by unwary Building Control officers, on the basis of compliance of the AOV alone.

The new, stricter regulation has removed this risk factor and has therefore made a positive contribution to the safety and reliability of modern AOVs.

BS EN 12101-2 test procedures

It’s reassuring to know that succesful EN12101-2 certification for AOVs should include cycle testing over many thousands of operations at high and low temperatures, with no more than a 10% reduction in opening area.

Units are tested to temperatures of 300ºC for thirty minutes and must be able to operate at least three times at –25ºC. If all EN2101- 2 test sections are carried out, the ventilators are also required to function under snow and wind loads, whilst opening fully in under 60 seconds, using back-up power.

To provide confirmation of testing and compliance, manufacturers must provide a Certificate of Conformity supplied by an accredited notified body. This provides details of the loadings and temperature ranges to which the AOV has been subjected to during testing and should always be accompanied by a Declaration of Performance.

As an active member of the SCA (Smoke Control Association), Lareine Engineering contributes to industrywide knowledge and understanding of smoke control in buildings and offers a complete range of high quality, compliant AOV solutions. The company manufactures its own range of AOV rooflights and hatches, as well as offering solutions through wellestablished partnerships with Kingspan Brakel and Windowmaster.

Lareine Engineering also offers a RIBA accredited CPD Seminar, entitled ‘Smoke: tackling the deadly enemy’. This can be booked here: https://lareineengineering.com/ downloads/riba-accredited-cpd/

www.lareineengineering.com

Typical modular AOV rooflight with integrated actuator mechanism to facilitate opening to 140º