Fire ventilation systems

According to the general laws of physics generated during a fire, smoke travels and spreads throughout the building due to the pressure difference caused:

• chimney effect
• wind
• day-to-day ventilation and air-condition operation system
• buoyancy of hot gases on storey covered by fire

In order to conduct thorough analysis of smoke flow directions, each of these factors should be taken into account and dealt with. However, in practice, due to the lack of detailed data related to weather conditions and conditions in the building (the size of the leak, the number of open doors and windows, etc.) which would have during a possible fire, a detailed analysis of all parameters is not usually possible.

The basic requirement for all types of ventilation systems is to protect against fire smoke evacuation routes, which is understood as a protection against the maintenance of these roads to smoke in an amount that due to limited visibility, or toxicity, would prevent the safe evacuation. This ensures safe evacuation of people and rescue teams access to the premises covered by the fire. In addition, the operation of these installations is to decrease the temperature of smoke and hot gases, which reduces the risk of flashover and reduces the destruction of equipment and building structure. Please note that due to technical limitations, fire ventilation requirements does not appear to remove the entire amount of smoke resulting from the fire or smoke protection against all the rooms in the building, and its scope is limited to certain space. According to the Life Safety Code requires that smoke-free space in atrium was at least 1.80 m from the floor, so that evacuating the people could walk under a layer of smoke accumulated under the ceiling.

Installation of fire ventilation should be started immediately after detecting a fire and function throughout the duration of the evacuation and fire fighting.

Technical solutions are individual fire ventilation for each building and strictly dependent on the type of construction, size and destination. They can be based both on natural and mechanical ventilation systems. They may be systems using smoke for an existing installation of ventilation in the building of housing, or independent fire ventilation systems that operate only in the event of fire.

There are three basic fire ventilation systems used in buildings:

• smoke prevent systems (called pressure differential systems) - to ensure the production of the pressure difference between the space covered by the fire and adjacent to a protected space, preventing ingress of smoke into the protected space;
• flow systems - causing restriction of movement of smoke through the air stream of sufficient velocity, the supply in the opposite direction to the incoming smoke;
• smoke removal systems - for the removal of smoke from the smoke-filled space (covered by the fire, or where the smoke is coming out) using a specially constructed for this purpose devices in a mechanical or natural. These systems are also used to create a negative pressure in smoky areas, preventing the escape of smoke from other zones.