Determination of the dilution of a gas discharged into a ventilated atmosphere

Abstract

A method was developed for measuring the dilution factor of a pollutant for any given conditions of ventilation. The method is based on injecting a pulse of radioactive gas into the flow of the pollutant and counting the activity at any desired point. The method, which is a shortcut to the use of continuous injection, has been employed in the investigation of the ventilation system to be used in the new Tel-Aviv Central Bus Station. Experiments were carried out in a test plant on bus exhaust gases at a flow rate of about 5 m 3/ min and dilution down to the range of 10 −4–10 −5. The activities employed were reasonably low and range from a few mCi up to a few tens of mCi 85Kr per injection.