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ISO 29904:2013 pdf free

ISO 29904:2013 pdf free.Fire chemistry – Generation and measurement of aerosols
Knowing how and where to sample the fire effluent is critical to obtaining an accurate and useful aerosol distribution. Thus, it is important to take into account the local transport processes that can result in non-uniform particle distributions.
The generation of particles begins within the flame or combustion zone in smouldering. Upon release into the fire atmosphere, agglomeration can occur to varying degrees. In the fire plume, because of thermophoresis (movement of particles due to a temperature gradient) and due to the upward,buoyancy-driven movement of the fire plume, particles will be entrained and carried initially upwards above the fire. Glowing carbon particles are the most important contributor to heat radiation from the fire plume, especially because these particles are typically present in a relatively high concentration, have an emissivity close to blackbody (i.e. radiate over a very large spectral range), and are present at high temperature.
Thermophoresis is a very important parameter governing the movement of aerosols in a hot fire and their deposition on any relatively cool surfaces. Thermophoretic movement may be considered as the mechanism by which the aerosols are repelled by a hot body and attracted to a cooler body resulting in a movement of particles and droplets from hot to cold areas. This results in the observed deposition of particles and droplets onto cool surfaces such as windows and walls in the structure containing the fire. Hot zones can be relatively free of particles, but are potentially capable of generating them if temperature conditions change. This is because, as the temperature drops, gaseous organic molecules can condense to form aerosols. In fact, the very act of sampling from these areas of apparently low or zero particles can give rise to measured particles through the intrusive (particularly cooling) effect of the measuring apparatus.ISO 29904 pdf download.

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