Disclosed are methods and apparatus for treating and analyzing a gas stream to determine the effectiveness of urea gasification. The apparatus will be capable of performing the method and will include: means for introducing an aqueous solution of urea into a reactor having hot gases therein and subjecting the aqueous to temperatures for a time to assure the gasification of the aqueous urea and form a thermal gasification product stream containing NH3 and HNCO; means for taking a sample stream from the gasification product stream; means for contacting the sample stream with a hydrolysis catalyst in the presence of sufficient water to convert HNCO to NH3 and form an ammonia sample stream; and means for analyzing the ammonia sample stream for NH3. The methods and apparatus can also be used to control a urea gasification process and/or to signal anomalous operation.