Bs 7346 Part 4 Pdf Free
CLICK HERE ->>> https://urllio.com/2taSNk
The tests in BS 7346 provide data of rates of smoke expulsion,the required flow rates of smoke exhaust, the smoke density, theworkload of the smoke exhaust and the radiation of heat in relationto the smoke density. These parameters are used to establish minimumand maximum flow rates of smoke exhaust for the specified dimensionsand conditions. In addition, the heat radiation is calculated todetermine the protection level required to ensure that it does notexceed a specified value. This information is used to formulaterequirements in BS 4368 for all such building types and occupanciesas described in BS 7246.
A second critical aspect of SHEVS performance is to avoid reducesthe radiation of heat to the outside environment. Smoke exhaustventilation systems are used to prevent the heat radiated fromthe smoke layer from exceeding a safe value. For this reason, smokeand heat exhaust ventilators must work reliably and efficiently,even in the presence of fire. Their effectiveness depends largelyon their design and the parameters specified in BS 7346.
For buildings of any height, the fire evacuation requirements areset out in BS 7246. Extensive guidance is also provided in BS 4368,which also covers such building types as basements, lofts, attheir tops, towers and atria.
The test data in this specification allows the smoke and heatexhaust ventilators to be specified to meet the requirements for a givenbuilding type, condition and size, when the fire exit routes arealone or in combination with other means of smoke evacuation.For the same building and fire conditions, the ventilator specifiedto meet the requirements of BS 4368 will perform better than theventilator specified to meet the requirements of BS 7246.
The term ‘free-area’ is defined in BS 7346-1 as the expentiallydefined area in front of a ventilator or collector that is theexposed surface of a wall at a building opening and, in the case ofan external ventilator, the width of the opening from which it discharges.
The coefficient of discharge is determined by multiplying thearea of the free-area of the ventilator or the collector designedto discharge the smoke by the average velocity of the flowthrough the ventilator or collector over a continuous timeperiod of one minute or over a continuous period of about 5minutes.
The calculation of the coefficient of discharge is complicatedby the influence of external side-winds. For this reason,BS 7346-1 defines the ‘effective coefficient of discharge’, which isa lower bound on the actual coefficient of discharge. Theeffect of external side-winds, however, is not taken into accountin the calculation of the effective coefficient of discharge.
The standard assumes that, where a smoke control damper is installedinthe fire-room, it is opened as a normal part of the firefighting operation(that is, prior to opening any smoke control vents).
A smoke control damper (SCD) is a valve that can be opened orclosed to control the flow of smoke and hot gases from the fire compartment.SCDs are used to control the flow of smoke from the fire compartmentso that the heat and smoke do not spread to other parts of thebuilding. 827ec27edc