Escape exits width

The formula (101) can also be proved with the escape-rate theory. We consider the escape of particles by difffusion from a large reservoir, as depicted in Fig. 17. The density of particles is uniform inside the reservoir and linear in the slab where diffusion takes place. The density decreases from the uniform value N/V of the reservoir down to zero at the exit where the particles escape. The width of the diffusive slab is equal to L so that the gradient is given by Vn = —N/ VL) and the particle current density J = —Wn = VN/ VL). Accordingly, the number of particles in the reservoir decreases at the rate... 

Minimum widths of escape routes and exits In terms of the width of the escape exits this again is a simple correlation between the numbers of persons who are likely to make use of the exits and the width of the doors and corridors. 

Table 10.2 summarises the flow rates of people through various exit widths, assuming that they have iy2 minutes to pass through the exit. The table demonstrates that flow rates increase with the increase of the available escape width. 

A subsequent research project found that although the exit widths were adequate for evacuation under normal conditions, when the need to escape became urgent the understandable panic significantly reduced the flow rates through the doors. 

Exit routes and doors from all facilities should be provided according to the requirements of NFPA 101. The minimum width of all exit routes should not be less than a standardized width, 1.0 meter (39 inches) being commonly adopted. Where low occupancy rooms are provided in offshore facilities near process areas, a secondary emergency escape hatch is provided as an alternative means of escape in addition to the normal means of egress. 

XPS spectra were recorded using unmonochromatized Mg K radiation (1253.6 eV), and an unmonochromatized He-resonance lamp was used for ultraviolet photoelectron spectroscopy (UPS). XPS spectra were taken with an analyzer resolution of 0.2 eV, and the net resolution measured as the full width at half-maximum (FWHM) of Au 4f(7/2) was 0.9 eV. The spectrometer is of our own construction and is, e.g., designed to provide optimum angle-dependent XPS or XPS(0) (12,l4). For high 5-values, the photoelectrons leave the sample surface near the grazing angel, and due to the limited escape depth of the electrons, this is a "surface sensitive" mode. In the "bulk sensitive" mode, for low 0-values, the photoelectrons exit near the surface normal, and hence more information from the "bulk" of the sample is obtained (15). 

The two key features in planning a means of escape are, firstly, the travel distance which is the distance a person must travel from any point within a floor area to the nearest exit to a protected stairway, escape route or to a place of safety. In general 18 m is considered to be the maximum travel distance if there is only one exit and 45 m if there is more than one. Secondly, except in special circumstances, at least two escape routes in substantially opposite directions should be provided for every storey or level of a building. The width of the exit and the escape route is governed by the number of people who may be present on the storey or level but the minimum permitted width is 826 mm. Where a corridor forms part of the travel distance it should be enclosed to restrict the spread of smoke. If the corridor is a dead end then it must have at least half-hour fire resistance walls and ceilings so that people can safely pass by a room if it is on fire. If the corridor connects alternative exits it should be fitted with smoke stop doors mid-way between the exits. 

The exit access is the pathway throngh the building that the occupants must follow in order to reach the discharge and safety. This path of travel must be clear of any obstruction that protrudes into the path. Water fountains, doors, displays, and cabinets should not restrict the width of the egress because the capacity of this pathway is essential to safe evacuation. Another important situation is the presence of dead ends that do not provide two ways of escape. These are strictly limited under NFPA 101 to 20 feet in educational occupancies without sprinklers and 50 feet in buildings with sprinklers (NFPA 101,2012). 

Furthermore, in order to afford all occupants convenient facilitates for escape, the capacity of an [exit route] (i.e., stair) for any occupied space must be appropriate to the individual building or structure with due regard to the character of the occupancy the number of persons exposed the fire protection available and the height and type of construction of the building or structure. [See paragraph 1910.36(b)(3).] The minimum width permitted for a passageway used as an exit access is, according to [ 1910.37(g)(2)], 28 inches however, most occupancies require additional width based upon the capacity of [exit route] requirements. 

The number, width and disposition of exits can then be provided and should be designed to allow 361 people to escape within the required time. 

In addition to the requirement to limit travel distances, it is also necessary to consider the flow of people through the exits from buildings. The Approved Document B provides guidance on the number and widths of exits that are required to provided an adequate means of escape. 

In practice this means that when planning or assessing the means of escape for a particular situation, there must be adequate numbers and widths of exit as well as adequate directions and distances of travel. 

Where two or more exits are provided from either a storey exit or on ground floor, it should be assumed that one of the exits may be compromised by fire thus preventing the occupants from using it. It is therefore essential that the remaining exit or exits are of sufficient width to allow all persons to escape in the available time. 

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