An AOV is an automatic opening ventilator which provides at least 1.0m2 of free area when open. In buildings of over 11 metres, there is a legal requirement to provide a means of protecting corridors and communal lobbies with access to the escape stairwell in order to control smoke. In these buildings AOVs are always installed at the highest point in an evacuation stairwell.
An AOV is designed to remove any smoke from the stairwells of small buildings, enabling an easier and safer exit. More commonly, they are installed in large buildings to provide replacement air for a lobby smoke extract system.
When a fire breaks out, smoke accumulates in communal lobbies or corridors adjoining the escape stairwell. Ventilation is a means of removing smoke from these areas.
This ventilation is provided through installing an AOV or a natural/mechanical smoke shaft system.
The horrific Grenfell tragedy in June 2017 sparked the requirement for a radical reform of building regulations. Dame Judith Hackett’s damning report ‘Building a Safer Future’, released in May 2018, looked at the regulatory framework around the construction, maintenance and ongoing use of buildings, focussing particularly on multiple occupancy, high-rise residential buildings. The report not only found that the existing regulations system was not fit for purpose, but that it also left room for short-cuts. The report set out 53 recommendations to establish a new regulatory framework and implement a culture change to create and maintain safe buildings. The government now aims to move from a passive system centred around compliance with building regulations to a proactive one – where developers and building owners take responsibility for ensuring that residents are safe.
Considering this imminent reform, high-rise building owners and developers are now reviewing their fire safety strategy to avoid another tragedy such as Grenfell.
Along with retrofitting AOV systems and testing and maintaining existing AOV systems, other fire safety measures include:
The failure of the smoke-control system in Grenfell Tower has been identified by experts as a factor in the building’s escape route filling with thick smoke, which in turn prevented evacuation and rescue. The system was designed to extract smoke from lobbies outside flats and protect the staircase.
Dr Barbara Lane, appointed by the Grenfell Tower Inquiry, produced a report investigating the fire protection measures in place on the night of the fire. Her findings concluded that the fire safety provisions within the single escape stairs and lobbies were designed to operate on one floor only – based on the assumption that fire would be contained in one flat. The smoke-control system in place could not have protected the staircase from smoke on multiple floors.
Because of the cladding fire a whole-building fire occurred, meaning the stairs and lobbies became the most important life-safety feature. Lane stated that the smoke-ventilation system design did not follow guidance in Fire Safety: Approved Document B (ADB) 2013 because it was a bespoke system, with evidence that it did not perform as designed, with automatic opening vents not closing correctly.
However, even if the AOV system had been installed and maintained compliantly to current regulations, it’s unlikely to have had much positive effect in the evacuation of the building as current statutory guidance requires the system to be effective only in a localised fire incident, not a whole building fire.
In light of this, the proposed overhaul of current building regulations is vital in protecting lives of occupants in the future. An effective AOV system installed and maintained correctly, along with a holistic fire safety strategy will undoubtedly afford better fire protection to residents of high-rise buildings in the future.
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