Fire Code of the Philippines Ebook - SafetySignsPH.com Fire Code of the Philippines eBook - SafetySignsPH | Page 428

containing the used water or waste water exposed to atmosphere, the
temperature of used water or waste water, the ambient air temperature,
and the vaporization rate of the volatile liquid. Allowance shall be made
for vaporization of volatile liquid from the free water surface in connecting
sewers within a reasonable distance from the structure, turbulence that
may accelerate vaporization of the volatile liquid, inefficiency of the
ventilation system in purging the enclosures, and any other factors that
the designer could reasonably expect to effect the rate of release of the
flammable vapour to the structure.
C. Ventilation rate shall conform to Table 33 which presents typical
ventilation rates for various areas in the treatment plants or shall be based
on actual calculations whichever is greater. In reference to the said
table, the following notes shall be considered:
1. The superscript (1) - prescribed the installation of combustible gas
detector and alarm system to monitor and provide warnings for the
explosive level of the confined combustible vapors.
2. The ventilation rates prescribed above are considered to be the
minimum necessary for protection against combustible vapors.
3. Ventilation rates shall be increased above those recommended if
unusual accumulations of volatile combustible liquid or combustible
vapors are expected or if toxic gases may be present.
Table 33: MINIMUM VENTILATION RATES IN
WATER AND WASTE WATER TREATMENT PLANTS
Description
Ventilation Rates
Wet wells, screen rooms, and other enclosed spaces
with used water or waste water exposed to
atmosphere (1)
Rooms or spaces intended for storage or conveyance
of used water or waste water solids, (e.g., grits, sludge,
hardened or cakes of fats and grease, etc.)
Equipment rooms, tunnels, and other below grade
spaces.
• With gas piping and/or gas handling equipment (1)
• With diesel fuel or other volatile combustible liquid
tanks, pumps and supply piping (1)
Without gas piping
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15 air changes
per hour
12 air changes
per hour
12 air changes
per hour or
40 km/min velocity
in tunnels or galleries
10 air changes
per hour or
27 km/min velocity in
tunnels or galleries