The main task of emergency ventilation
During a fire, to remove smoke, use air-handling units that supply air to evacuation passages and staircases. When the toxic substances are released into the room, the air enters the room as a result of its flow from adjacent rooms.
In order to calculate the required air exchange in emergency mode, it is necessary to take into account the non-stationary nature of the process when solving the gas balance equation in the room, which is recorded in differential form.
An emergency situation can occur due to various reasons: fire, spontaneous combustion, sudden release of gas, explosion, etc. For this, there must be a special plan for the operating modes of auxiliary ventilation plants in the event of an accident.
Typology of emergency ventilation
There are several types of emergency ventilation :
- Extraction general ventilation systems with additional fans for air flow in the event of an accident;
- Emergency exhaust systems in addition to the main systems( with a spare fan), if the waste of air in them does not ensure the exchange of air in full;
- Exceptionally emergency exhaust ventilation systems, if the application of the main systems is impractical or impossible;
- Exceptionally emergency ventilation systems for single-storey houses.
Ventilation devices must be located: to remove the gases and vapors that have a specific gravity greater than the specific gravity of the air in the working part of the room, and a smaller specific gravity in the upper zone. To prevent smoke use smoke smoke emergency ventilation to evacuate people from the premises during a fire that has just arisen.
In some cases, a spare unit is put. He is associated with the machine. When the worker is turned off, the backup is automatically turned on. Devices that trigger emergency ventilation should be installed at the entrance doors.
This ventilation is always ready, and it has two modes of operation:
- Active. The development of emergency ventilation is sufficient throughout the entire emergency situation, and the content of harmful substances in the air remains at a safe level;
- Passive. The lack of emergency ventilation, and the accumulation of vapors and gases in the air is constantly growing and goes beyond the safe level. Safety of operation in this mode is not guaranteed, because any impulse can cause explosion of the formed mixture of gases.
Features of emergency ventilation calculation
Calculation of emergency ventilation is based on the following parameters:
- air flow velocity in ducts - m / s and working pressure - Pa;
- permissible noise level - dB;
- air capacity - m³ / h;
- power of the heater - kW.
The indicator is regulated by sanitary and building codes and regulations. It is better, if the calculation will be carried out by a specialist, as doing it yourself is quite difficult. There are some requirements for emergency ventilation systems:
- The air that is drawn should go out on the street above the roof, while the duct of the duct can run both outside and inside the building;
- Fresh air must pass through a grate placed no less than 2 meters above the ground;
- The movement of air must be arranged so that it leaves the living rooms in the direction of the bathroom, kitchen or bathroom.
