What Are the Best Methods for Smoke Ventilation?

The mechanical smoke exhaust is to use the smoke exhaust machine to exhaust the smoke and heat generated in the fired room to the outdoor through the smoke exhaust port, while forming a negative pressure in the fire area to prevent the smoke from spreading to other areas.

Exhaust smoke using mechanical (fan) force is called mechanical smoke exhaust, fire area

Mechanical exhaust: local exhaust and centralized exhaust.

Local smoke exhaust method: An independent smoke exhaust fan is installed at each part where smoke is required to directly exhaust smoke.

Centralized smoke exhaust method: Divide the building into several districts, set up smoke exhaust fans in each district, and exhaust smoke through the smoke exhaust fans.

In a nutshell, a mechanical smoke exhaust system should be installed wherever smoke exhaust facilities are not available, and where natural smoke exhaust conditions are not available. Specifically, according to the High Regulations, mechanical smoke extraction facilities shall be provided in the following locations of Class I high-rise buildings and Class II high-rise buildings with a building height exceeding 32m:

(1) No inner aisle with direct natural ventilation and a length exceeding 20m or an inner aisle with a length exceeding 60m although there is direct natural ventilation;

(2) Floorless rooms or rooms with fixed windows that have an area of more than 100m ² and often have people staying or have a lot of combustible materials;

(3) Atriums that do not have natural smoke exhaust conditions or have a clear height of more than 12m;

(4) Except for rooms that use windows such as window wells for natural smoke exhaustion, basement rooms with a total area of more than 200m ² or a room with an area of more than 50m ² , and often have people staying or have more combustible materials;

(5) Smoke-resistant staircases and podiums of high-rise buildings with podiums, front rooms of fire-fighting elevators, or shared front rooms. When the podium is opened above the podium, natural smoke can be exhausted, while the podium is not In the smoke exhaust condition, the front room or shared front room should be provided with a local positive pressure air supply system, and the positive pressure value should be guaranteed to 25-30Pa;

(6) Mechanical smoke extraction systems should also be installed in places where people are concentrated in shopping malls, restaurants, public entertainment venues, and where there is a lot of combustibles. The garage should also be equipped with a mechanical smoke exhaust system.

(1) The smoke exhaust openings of the front room, walkway and room where mechanical smoke exhaust is installed shall be provided on the ceiling or the wall near the ceiling. The smoke exhaust openings shall be closed normally. The smoke mouth should be provided with a manual automatic opening device, and the operating part of the manual opening device should be set at 0.8 ~ 1.5m from the ground. The smoke exhaust port and the exhaust valve should be interlocked with the exhaust fan. When any of the exhaust ports or the exhaust valve is opened, the exhaust fan can be started;

(2) The horizontal distance between the smoke exhaust port and the furthest point of the smoke prevention zone should not exceed 30m;

(3) The exhaust fan can be a common steel centrifugal fan or a special exhaust axial fan, and a fire valve that can be automatically closed at 280 ° C should be installed on the fan inlet main pipe and the exhaust pipe;

(4) The mechanical smoke exhaust system should be installed separately, and can be used with the usual ventilation and exhaust system when conditions permit;

(5) Non-combustible materials must be used for the air pipes, vents, valves, and ventilators of the mechanical smoke extraction system, and the distance from the combustibles must not be less than 15cm. The thickness of the steel plate of the exhaust pipe should not be less than 1.0mm;

(6) The maximum allowable wind speed of all mechanical smoke prevention and exhaust systems is adopted according to Table 1 below;

Table 1 Allowable maximum wind speed of mechanical smoke exhaust system

Air duct and air outlet category	Allowable maximum wind speed (m / s)
Metal duct	20
Smooth internal air duct	15
Smoke exhaust	10
Outlet	7

(7) The mechanical smoke prevention and exhaust system should be regularly overhauled and operated to ensure timely startup in emergency situations. ^[2]