Natural smoke ventilation systems
Within residential buildings there are typically 2 different types of system, stairwell only ventilation and protected lobby ventilation.
Protected Lobby Ventilation
Designed to extract any smoke leaking into a common lobby to protect the escape stairs.
Typically, a vertical duct rising through the building would be used to extract smoke from the lobby, each lobby would have a damper connected to the duct, the head of the shaft is terminated with an automatic opening ventilator (AOV), alternatively vents can be mounted on outer walls leading directly to fresh air, In both cases an AOV would also be mounted at the top of the stairwell
Controlled by an interconnected system that provides automatic operation of the smoke ventilation system via operation of a smoke detector within the protected lobby.
Stairwell Ventilation
Stairwell ventilation (AOV) serves one of two purposes;
- To extract any smoke that gets in the stairwell of small buildings.
- Provides replacement air for a lobby smoke extract system in large buildings.
Mechanical smoke ventilation systems
Designed to extract any smoke leaking into a common lobby to protect the escape stairs.
Typically, a vertical duct rising through the building would be used to extract smoke from the lobby, each lobby would have a damper connected to the duct with a set of smoke extract fans located at roof level with an AOV mounted at the top of the stairwell.
Controlled by an interconnected system that provides automatic operation of the smoke ventilation system via operation of a smoke detector within the protected lobby.
Mechanical ventilation systems allow a reduction in the size of shaft area compared to a natural ventilation system providing a saving on lettable space within the development and removing the risk of wind or negative heat effects limiting the effectiveness of the passive ventilation system.
Car park ventilation systems
The ventilation of car parks is important to prevent the build-up of toxic fumes and flammable gases from motor exhausts, and to clear smoke in the event of a fire.
The Building Regulations (in particular Approved Document B and Approved Document F) specify what is required to maintain safe conditions in a car park. Further guidance is also given in BS 7346-7:2013.
There are broadly two methods of complying with the Building Regulations regarding ventilation and these are natural or mechanical ventilation. Whichever method is used, the required results are defined as:
Smoke clearance
To provide sufficient openings for enclosed car parks to allow any smoke being produced to leave the space naturally, or if this cannot be achieved then to remove smoke via a mechanical extract system.
The Requirements
Fume exhaust
To provide sufficient openings arranged such that a through draught at low/mid level is created to allow CO to leave the car park naturally, or if this cannot be achieved then to limit the concentration of CO within the space via a mechanical extract system.
