ISO 29904-2013 pdf free download

ISO 29904-2013 pdf free download.Fire chemistry Generation and measurement of aerosols
Chimie de Ia combustion — Production et mesurage des aerosols.
on the visibility in smoke-filled spaces. It has been suggested that above a certain opacity of smoke, many would consider that escape would be seriously impeded. See Annex D for further details.
b) In fire modelling, soot yield is an important input parameter. It has a very significant effect on the heat radiation properties of flames (often a sub-model of the main model), and therefore on the general heat transfer by radiation, which can affect escape from a lire (see ISO 13571) and can significantly influence fire growth and the occurrence of”f lashover”. See Annex D for further details.
c) The direct physiological effect of aerosols on people is related to the size fractions within the aerosol and the morphology of the particles and droplets. It is therefore often more important to know the particle and aerosol distribution by size rather than the total aerosol mass for the determination of physiological effects. Unfortunately, size distribution is a parameter, which is often difficult to measure, principally due to the processes of agglomeration over short time intervals. Agglomeration can greatly affect the structure of the particles and droplets, as well as their density and optical (i.e. obscuration) properties. In addition, volatile species that may evaporate to a varying degree while being sampled and measured will influence the data recorded. Furthermore, measuring instrunwnts operating on different principles will give different effective size fractions, and the methods cannot be assumed to be equivalent. The main parameter to consider for physiological effect of aerosols is their deposition in the respiratory tract. Different classes of particle size, based on their relation to physiological effects, have been defined: “PM10, “PM2.5”, “inhalable” (D < 100 pm). “thoracic (D < 10 pm), respirahle” (D < 4 pm), “ultrafine’ (D < 0,1 pm), and “nanoparticulates” (D 0,050 pm). See Annex C for further details.
Mass concentration and particle and droplet size fraction can also be valuable parameters for computational fluid dynamics (CFD) computer modelling of fire processes. This is especially true as nrndels become capable of simulating the evolution of the aerosols and the effects of the evolution on flame radiation.
4.2 Movement and evolution of fire aerosol
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.ISO 29904-2013 pdf free download.