Back draft ( draft tipping ) - the absence of rarefaction in the smoke or ventilation duct, which prevents the removal of combustion products from operating devices (stove, fireplace, stove, boiler, column, etc.) or the removal of exhaust air from the room into the atmosphere.
With reverse draft in the chimney, emissions of combustion products into the room are observed, and smoke and gases can also come through ventilation and smoke channels both from operating devices located in this room, and from other rooms from devices installed in other rooms and apartments. In this case, there is a serious danger of carbon monoxide poisoning (up to death) and fires.
Reasons for Backdraft
- The location of the mouth of the chimney (ventilation) pipe in the zone of the wind shadow (the so-called "zone of wind backwater") formed by the ridge of the building (protruding parts of buildings and tall trees);
- A sharp gusty (hurricane) wind of a certain strength and direction;
- The presence in the channels of cold air and a high content of water vapor, preventing the occurrence of traction;
- The presence of blockages in the channels (bird nests, soot deposits, accumulation of debris);
- Incorrect design of the channels (the presence of constrictions and extensions, rolls, inclinations and incorrect tips);
- Freezing, freezing and blocking of channels with snow, frost-like mass;
- The presence of drafts and indoor air movements caused by the combination of large rooms and the lack of division into compartments;
- Destruction of the pipe or channel spatter;
- Insufficient air flow (with sealed windows installed without supply valves), insufficient cross-sectional area for the flow of the required amount of air, or caused by the operation of exhaust systems (primarily kitchen hoods ), fans and compressors.
Remedies
- The extension of the pipe and its removal above the zone of the wind shadow;
- Termination of the furnace;
- Drying and heating channels;
- Regular and emergency cleaning of channels;
- Relocation and correction of the design of the channels.
- Heating and freezing clearing. (thermal insulation of channels and temperature control of exhaust gases)
- Redevelopment and separation of the premises (installation of doors and organization of directed flows);
- Repair and relocation of damaged areas, or the entire structure.
- Removing redundant appliances and establishing the isolation of the room. Increase in air size.
- Inadmissibility of the use of exhaust hoods in the air removal mode and fans in conjunction with appliances, with the removal of combustion products into the chimney (boilers, columns).
- Ensuring the flow of fresh outdoor air necessary for normal combustion.
Backdraft (fire term)
Reverse thrust is a phenomenon that can occur during a fire in enclosed spaces under conditions when the fire , experiencing a lack of oxygen , dies out, while gaseous combustible products of incomplete combustion accumulate in the room ( carbon monoxide , pyrolysis products [1] ) [2] . When fresh air is available , for example, when a door is opened into a room, lightning-like explosive inflation of the fire occurs with the release of hot gases. Dangers from the outside can be recognized by yellow or brown smoke, whose color is due to incomplete combustion seeping through slots or exhaust openings.
Firefighters prevent back draft by allowing smoke and flame to disperse.
A frivolous or unprofessional attitude to the “backdraft” can cause the death of both ordinary people and firefighters [3] .
See also
- Back thrust (film)
Notes
- ↑ Fire // Great Soviet Encyclopedia : [in 30 vol.] / Ch. ed. A.M. Prokhorov . - 3rd ed. - M .: Soviet Encyclopedia, 1969-1978.
- ↑ Fires of the big city / 05/19/2010, " Around the World ". Sergey Kutovoy .
- ↑ Opening doors in case of fire / Article on the site of ANO DPO "Training and Consulting Center for Rescue Units".