A gas is termed as non-toxic, if its maximum permissible concentration (TLV) ranges from ______________ ppm?
(A) 1000 to 2000
(B) 3000 to 6000
(C) 6000 to 9000
(D) 10000 to 100000
Noise level heard inside a bus in busy city traffic or inside a sub-way train corresponds to about ______________ decibels?
(A) 75
(B) 95
(C) 120
(D) 140
Main pollutant present in automobile exhaust is_________________?
(A) CO
(B) CO2
(C) NO
(D) Hydrocarbons
Scale formation in boiler is controlled by____________________?
(A) Preheating of feed water
(B) Reduction in hardness, silica & alumina in feed water
(C) Keeping the pH value of feed water just below 7
(D) Eliminating H2S in feed water
Noise level heard at a distance of about 100 metres from a jet engine with after burner is about _____________ decibels?
(A) 120
(B) 140
(C) 170
(D) 200
Presence of bacteria in potable (drinking) water causes_________________?
(A) Turbidity
(B) Disease
(C) Bad odour
(D) Bad taste & colour
TLV of ozone (O3) and phosgene (COCl2) in air is _______________ ppm?
(A) 0.1
(B) 25
(C) 100
(D) 1000
Radioactive substances present in the polluted water stream can be removed by_________________?
(A) Biological oxygen treatment
(B) Coagulation and filtration
(C) Adsorption in ion exchange materials
(D) None of these
H2S present in gaseous stream can be removed by adsorption on _____________________?
(A) Silica gel
(B) Active carbon
(C) Bog iron
(D) Limestone powder