Abstract
There are many areas in which existing local exhaust ventilation design criteria, control methods, and maintenance of control could be improved. Current practice, based on quite old data, requires close scrutiny against changing conditions and advances in technology. Innovations during such an interval often go unnoticed; they deserve more extensive reporting if the practice of exhaust ventilation is to be improved. The prdblems of high-speed grinder control, hot operation exhaust, operating cost reduction, the use of air jets, and exhaust system maintenance are discussed.