232. On prolonged exposure to high concentration of carbon monoxide (> 5000 ppm), man dies because
234. A considerable part of the harmful ultraviolet radiation of the sum does not reach the earth surface, because of the fact that, there is a layer of __________ high above earth's atmosphere, which absorbs it.
235. Maximum permissible concentration (i.e. TLV) of DDT in public water supply system is __________ micro gram (μ g)/litre.
237. In a sedimentation tank, the detention period for water ranges from __________ hours.
238. Water filtration rate in a rapid sand filter ranges from __________ kilolitres/m2/hr.
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