Evaluation of the emission rate from a gaseous source: Development of a method using a helium tracer

A tracer gas (helium) has been used to determine the emission rate of a gas eous pollutant source of acetone. The method principle consists of measurin g the pollutant concentration in the vicinity of the source and the polluta nt transfer coefficient determined with the tracer gas. The ratio of the po llutant concentration by the tracer gas transfer coefficient gives the poll utant emission rate. The study demonstrates the validity of the tracer gas method for determining the emission rate of a pollutant source comprising a solvent bath. Nevertheless, limitations were highlighted when the source w as placed in very still air (air velocity above the bath less than 10 cm/se c approximately). For that particular ventilation condition it was difficul t to have a tracer emission representative of that of the pollutant source due to the high fluctuations of the pollutant emission rate. On the other h and, the helium and acetone transfer coefficients have been found equals wh atever the ventilation in the vicinity of the solvent bath, when the tracer emission gives a true representation of the pollutant source. This method is intended to be used for on-site measurements of gaseous pollutant emissi on rates such as solvents or acids emitted from surface treatment tanks.