The Characteristics of Smoke Ventilation in Commercial and Industrial Buildings
Louvered windows are a common feature in commercial and industrial buildings. Located at high level, they are predominately used to afford natural ventilation flows around the building. Depending on the age of the building, the design of the building and the number of people the building caters for, the windows may be operated by the following:
High level venting louvered windows are available in several different designs with varying features. Louvers can be opened singly or in multiples. It is not unusual for eclectically operated controls to be coupled to smoke alarms and fire detection systems. In the event of smoke or fire, the high level vents will open automatically for rapid evacuation of smoke, heat and fumes.
SMOKE AND WATER
Water will always find the lowest level and, until it does, will always flow in a downward motion. Once water finds a level which it cannot go beyond water will begin to pool. The most natural pooling is of course lakes, seas and oceans.
Smoke on the other hand will always travel upwards and accumulate at a high level. This is because smoke is hotter than the surrounding air. Because it is hotter it is lighter; natural convection currents will flow upwards. Like water, once smoke finds a level which it cannot flow past, it will accumulate.
As smoke accumulates it will become denser, more acrid and by definition more toxic. Window vents at a high level in a building allow the smoke to flow through. If the smoke is unable to escape to atmosphere, it will become hotter which will compound the danger. Opening the high level vents allows the smoke to escape and disperse to atmosphere.
SMOKE MANAGEMENT
Smoke management in industrial, commercial and public buildings varies from country to country, governed by codes and building regulations. The purpose of smoke management is to create a layer which is above the level in the building where people work or congregate. There are two different methods of smoke ventilation.
Natural ventilation relies on windows located either in the roof or at the highest levels of open spaces, with natural air flows taking the smoke up and out of the building. Naturally occurring convection currents will take the hot smoke up the natural ventilation path and out in to atmosphere. Architects, builders and other stakeholders rely on the help and advice of fire brigade professionals and other experts when designing and installing smoke management systems.
This system is reliant on high level venting windows being opened as soon as there is an indication of fire or smoke. Systems can be manually operated via window openers at a lower level which are connected to a winding handle at a lower level. Electric window openers can be – and often are – connected to smoke detection systems and fire alarm systems, so they can be initiated automatically without the need for human intervention.
Alternatively, smoke evacuation from a building can be expedited by roof mounted fans, either as a standalone system or one which works in tandem with vents.
The shape of the building, the height of the building and the number of opening windows and their locations can have cause variations in air pressure within the building. The pressure within the building can also be affected by the smoke due to expansion. Also, the direction of the wind, wind speed and other naturally occurring events will dictate where, how and when windows and vents are utilised.