well as other pollutants said prem mishra the captain of a team that has designed an allterrain racing car at first the students experimented by using goats urine which is known to be rich in ammonia however it was difficult to find the liquid in adequate quantity so they switched to using ammonium hydroxide nh4oh instead the fumes are passed through a venturi a pipe which has a small section that has been constricted when the fumes pass through the constricted section they travel at a high velocity at this point the nh4oh is sprayed and the fumes are neutralized he explained